Light-Emitting Element, Light-Emitting Device, Electronic Device, and Lighting Device

ABSTRACT

To provide a light-emitting element with high emission efficiency. In a light-emitting element including an organic compound between a pair of electrodes, the molecular weight X of the organic compound is 450 or more and 1500 or less, and the absorption edge of the organic compound is at 380 nm or more. By liquid chromatography mass spectrometry in a positive mode in which an argon gas is made to collide with the organic compound subjected to separation using a liquid chromatograph at any energy higher than or equal to 1 eV and lower than or equal to 30 eV, a product ion is detected at least around m/z=(X−240).

This application is a continuation U.S. application Ser. No. 14/088,690,filed on Nov. 25, 2013 which is incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a light-emitting element usingelectroluminescence (EL). Further, the present invention relates to anorganic compound included in the light-emitting element. Furthermore,the present invention relates to a light-emitting device, an electronicdevice, and a lighting device each of which includes the light-emittingelement.

2. Description of the Related Art

In recent years, research and development have been extensivelyconducted on light-emitting elements utilizing EL. In a basic structureof such a light-emitting element, a layer containing a light-emittingsubstance is interposed between a pair of electrodes. By applyingvoltage to this element, light emission from the light-emittingsubstance can be obtained.

Such light-emitting elements are self-luminous elements and haveadvantages over liquid crystal displays in having high pixel visibilityand eliminating the need for backlights, for example; thus, suchlight-emitting elements are thought to be suitable for flat paneldisplay elements. The light-emitting elements also have a greatadvantage that they can be manufactured as thin and lightweightelements. Further, very high-speed response is also one of the featuresof such elements.

Further, since such a light-emitting element can be formed in a filmfoim, planar light emission can be easily obtained. Therefore,large-area elements utilizing planar light emission can be easilyformed. This feature is difficult to obtain with point light sourcestypified by incandescent lamps and LEDs or linear light sources typifiedby fluorescent lamps. Thus, the light-emitting element also has greatpotential as a planar light source applicable to a lighting device andthe like.

The light-emitting elements utilizing EL can be broadly classifiedaccording to whether they use an organic compound or an inorganiccompound as a light-emitting substance. In the case where an organiccompound is used as the light-emitting substance, application of avoltage to a light-emitting element causes injection of electrons andholes into a layer that includes the organic compound from a pair ofelectrodes, and thus a current flows. Then, the injection of thesecarriers (the electrons and holes) makes the organic compound to form anexcited state and to emit light when it returns from the excited stateto a ground state.

With such a mechanism, such a light-emitting element is called acurrent-excitation light-emitting element. Note that the excited stateformed by an organic compound can be a singlet excited state or atriplet excited state, and luminescence from the singlet excited stateis referred to as fluorescence, and luminescence from the tripletexcited state is referred to as phosphorescence.

In improving element characteristics of such a light-emitting element,there are a lot of problems which depend on a substance, and in order tosolve the problems, improvement of an element structure, development ofa substance, and the like have been carried out (for example, seeNon-Patent Document 1).

REFERENCE Non-Patent Document

[Non-Patent Document 1] Meng-Huan Ho, Yao-Shan Wu and Chin H. Chen, 2005SID International Symposium Digest of Technical Papers, Vol. XXXVI. pp.802-805.

SUMMARY OF THE INVENTION

An object of one embodiment of the present invention is to provide alight-emitting element with high emission efficiency. Further, an objectis to provide a light-emitting device, an electronic device, or alighting device with low power consumption.

A light-emitting element of one embodiment of the present inventionincludes an organic compound having a phenylcarbazole skeleton. Theorganic compound has a high hole-transport property. Thus, when theorganic compound is used for a light-emitting element, a light-emittingelement having high emission efficiency can be obtained. Further, alight-emitting element in which increase of driving voltage issuppressed can be obtained.

One embodiment of the present invention is a light-emitting elementincluding an organic compound between a pair of electrodes. Themolecular weight X of the organic compound is greater than or equal to450 and less than or equal to 1500. The absorption edge of the organiccompound is at 380 nm or more. By liquid chromatography massspectrometry (abbreviation: LC/MS analysis) in a positive mode in whichan argon gas is made to collide, at any energy higher than or equal to 1eV and lower than or equal to 30 eV, with the organic compound subjectedto separation using a liquid chromatograph (also referred to as LCseparation), a product ion is detected at least around m/z=(X−240).

Note that in this specification, m/z refers to a mass-to-charge ratio.In this specification, a positive mode refers to a mode in which apositive ion is detected. In this specification, a product ion refers toan ion generated by dissociation of an organic compound or an ionthereof in LC/MS analysis or analysis with a time-of-flight secondaryion mass spectrometer (TOF-SIMS).

One embodiment of the present invention is a light-emitting elementincluding an organic compound between a pair of electrodes. Themolecular weight of the organic compound is 486. The absorption edge ofthe organic compound is at 380 nm or more. By LC/MS analysis in apositive mode in which an argon gas is made to collide with the organiccompound subjected to LC separation at any energy higher than or equalto 1 eV and lower than or equal to 30 eV, a product ion is detected atleast around m/z=246.

One embodiment of the present invention is a light-emitting elementincluding an organic compound between a pair of electrodes. Themolecular weight of the organic compound is 562. The absorption edge ofthe organic compound is at 380 nm or more. By LC/MS analysis in apositive mode in which an argon gas is made to collide with the organiccompound subjected to LC separation at any energy higher than or equalto 1 eV and lower than or equal to 30 eV, a product ion is detected atleast around m/z=322.

Here, for example, “around 246” includes at least a range of greaterthan or equal to 243.5 and less than 248.5. That is, in thisspecification, “around N” (N is an integer) includes a numeric valuegreater than or equal to (N−2.5) and less than (N+2.5).

One embodiment of the present invention is a light-emitting elementincluding an organic compound between a pair of electrodes. Themolecular weight of the organic compound is greater than or equal to 450and less than or equal to 1500. The absorption edge of the organiccompound is at 380 nm or more. The organic compound includes aphenylcarbazole skeleton and an N-biphenyl-N-phenylamine skeleton. ByLC/MS analysis in a positive mode in which an argon gas is made tocollide with the organic compound subjected to LC separation at anyenergy higher than or equal to 1 eV and lower than or equal to 30 eV, aproduct ion of m/z derived from at least the N-biphenyl-N-phenylamineskeleton is detected.

One embodiment of the present invention is a light-emitting elementincluding an organic compound between a pair of electrodes. Themolecular weight of the organic compound is greater than or equal to 450and less than or equal to 1500. The absorption edge of the organiccompound is at 380 nm or more. The organic compound includes aphenylcarbazole skeleton and an N,N-bis-biphenylamine skeleton. By LC/MSanalysis in a positive mode in which an argon gas is made to collidewith the organic compound subjected to LC separation at any energyhigher than or equal to 1 eV and lower than or equal to 30 eV, a production of m/z derived from at least the N,N-bis-biphenylamine skeleton isdetected.

In each of the above-described structures, a product ion may be detectedat least around m/z=243 in a qualitative spectrum (a positive ion) ofthe organic compound measured with a TOF-SIMS in which Bi₃ ⁺⁺ is used asa primary ion and the amount of irradiation with the primary ion isgreater than or equal to 8×10¹⁰ ions/cm² and less than or equal to1×10¹² ions/cm².

It is preferable that the light-emitting element with any of theabove-described structures include a hole-injection layer, ahole-transport layer, and a light-emitting layer and that the organiccompound be included in at least one of the hole-injection layer, thehole-transport layer, and the light-emitting layer.

One embodiment of the present invention is a light-emitting deviceincluding any of the above-described light-emitting elements of oneembodiment of the present invention in a light-emitting portion. Oneembodiment of the present invention is an electronic device includingthe light-emitting device in a display portion. One embodiment of thepresent invention is a lighting device including the light-emittingdevice in a lighting portion.

The light-emitting element of one embodiment of the present inventionhas high emission efficiency, and thus, a light-emitting device with lowpower consumption can be obtained. In a similar manner, an electronicdevice and a lighting device with low power consumption can be obtainedby adopting one embodiment of the present invention.

Note that the light-emitting device in this specification includes animage display device that uses a light-emitting element. Further, thecategory of the light-emitting device in this specification includes amodule in which a light-emitting element is provided with a connectorsuch as an anisotropic conductive film or a TCP (tape carrier package);a module including a TCP which is provided with a printed wiring boardat the end thereof; and a module in which an IC (integrated circuit) isdirectly mounted on a light-emitting element by a COG (chip on glass)method. Furthermore, light-emitting devices that are used in lightingequipment and the like shall also be included.

In one embodiment of the present invention, the molecular weight X of anorganic compound is greater than or equal to 450 and less than or equalto 1500, the absorption edge of the organic compound is at 380 nm ormore, and a product ion is detected at least around m/z=(X−240) by LC/MSanalysis in a positive mode in which an argon gas is made to collidewith the organic compound subjected to LC separation at any energyhigher than or equal to 1 eV and lower than or equal to 30 eV.

For example, in one embodiment of the present invention, the molecularweight X of an organic compound is 486, the absorption edge of theorganic compound is at 380 nm or more, and a product ion is detected atleast around m/z=246 in LC/MS analysis in a positive mode in which anargon gas is made to collide with the organic compound subjected to LCseparation at any energy higher than or equal to 1 eV and lower than orequal to 30 eV. Further, in one embodiment of the present invention, themolecular weight X of an organic compound is 562, the absorption edge ofthe organic compound is at 380 nm or more, and a product ion is detectedat least around m/z=322 by LC/MS analysis in a positive mode in which anargon gas is made to collide with the organic compound subjected to LCseparation at any energy higher than or equal to 1 eV and lower than orequal to 30 eV.

In one embodiment of the present invention, the molecular weight of anorganic compound is greater than or equal to 450 and less than or equalto 1500, the absorption edge of the organic compound is at 380 nm ormore, the organic compound includes a phenylcarbazole skeleton and anN-biphenyl-N-phenylamine skeleton, and, by LC/MS analysis in a positivemode in which an argon gas is made to collide with the organic compoundsubjected to LC separation at any energy higher than or equal to 1 eVand lower than or equal to 30 eV, a product ion of m/z derived from atleast the N-biphenyl-N-phenylamine skeleton is detected. In anotherembodiment of the present invention, the molecular weight of an organiccompound is greater than or equal to 450 and less than or equal to 1500,the absorption edge of the organic compound is at 380 nm or more, theorganic compound includes a phenylcarbazole skeleton and anN,N-bis-biphenylamine skeleton, and, by LC/MS analysis in a positivemode in which an argon gas is made to collide with the organic compoundsubjected to LC separation at any energy higher than or equal to 1 eVand lower than or equal to 30 eV, a product ion of m/z derived from atleast the N,N-bis-biphenylamine skeleton is detected.

In each of the above-described organic compounds, a product ion may bedetected at least around m/z=243 in a qualitative spectrum (a positiveion) of the organic compound measured with a TOF-SIMS in which Bi₃ ⁺⁺ isused as a primary ion and the amount of irradiation with the primary ionis greater than or equal to 8×10¹⁰ ions/cm² and less than or equal to1×10¹² ions/cm².

By use of one embodiment of the present invention, a light-emittingelement having high emission efficiency can be provided. Further, by useof one embodiment of the present invention, a light-emitting device, anelectronic device, or a lighting device with low power consumption canbe provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D show examples of a light-emitting element.

FIGS. 2A and 2B show an example of a light-emitting device.

FIGS. 3A to 3C show examples of a light-emitting device.

FIGS. 4A to 4E show examples of an electronic device.

FIGS. 5A and 5B show examples of a lighting device.

FIG. 6 shows a light-emitting element of Example.

FIG. 7 shows voltage vs. luminance characteristics of a light-emittingelement of Example 1.

FIG. 8 shows luminance vs. current efficiency characteristics of thelight-emitting element of Example 1.

FIG. 9 shows voltage vs. current characteristics of the light-emittingelement of Example 1.

FIG. 10 shows luminance vs. chromaticity characteristics of thelight-emitting element of Example 1.

FIG. 11 shows an emission spectrum of the light-emitting element ofExample 1.

FIG. 12 shows voltage vs. luminance characteristics of a light-emittingelement of Example 2.

FIG. 13 shows luminance vs. current efficiency characteristics of thelight-emitting element of Example 2.

FIG. 14 shows voltage vs. current characteristics of the light-emittingelement of Example 2.

FIG. 15 shows luminance vs. chromaticity characteristics of thelight-emitting element of Example 2.

FIG. 16 shows an emission spectrum of the light-emitting element ofExample 2.

FIG. 17 shows the result of a reliability test of the light-emittingelement of Example 2.

FIG. 18 shows voltage vs. luminance characteristics of a light-emittingelement of Example 3.

FIG. 19 shows luminance vs. current efficiency characteristics of thelight-emitting element of Example 3.

FIG. 20 shows voltage vs. current characteristics of the light-emittingelement of Example 3.

FIG. 21 shows luminance vs. chromaticity characteristics of thelight-emitting element of Example 3.

FIG. 22 shows an emission spectrum of the light-emitting element ofExample 3.

FIG. 23 shows voltage vs. luminance characteristics of a light-emittingelement of Example 4.

FIG. 24 shows luminance vs. current efficiency characteristics of thelight-emitting element of Example 4.

FIG. 25 shows voltage vs. current characteristics of the light-emittingelement of Example 4.

FIG. 26 shows luminance vs. chromaticity characteristics of thelight-emitting element of Example 4.

FIG. 27 shows an emission spectrum of the light-emitting element ofExample 4.

FIGS. 28A and 28B are ¹H NMR charts of an organic compound representedby a structural formula (100).

FIGS. 29A and 29B show ultraviolet-visible absorption spectra andemission spectra of the organic compound represented by the structuralformula (100).

FIGS. 30A and 30B show results of LC/MS analysis of the organic compoundrepresented by the structural formula (100).

FIGS. 31A and 31B show results of TOF-SIMS measurement of the organiccompound represented by the structural formula (100).

FIGS. 32A and 32B show results of TOF-SIMS measurement of the organiccompound represented by the structural formula (100).

FIGS. 33A and 33B are ¹H NMR charts of an organic compound representedby a structural formula (101).

FIGS. 34A and 34B show ultraviolet-visible absorption spectra andemission spectra of the organic compound represented by the structuralformula (101).

FIGS. 35A and 35B show results of LC/MS analysis of the organic compoundrepresented by the structural formula (101).

FIGS. 36A and 36B show results of TOF-SIMS measurement of the organiccompound represented by the structural formula (101).

FIGS. 37A and 37B show results of TOF-SIMS measurement of the organiccompound represented by the structural formula (101).

FIGS. 38A and 38B show results of LC/MS analysis of an organic compoundrepresented by a structural formula (200).

FIG. 39 shows ultraviolet-visible absorption spectra of the organiccompounds represented by the structural formulae (100), (101), and(200).

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to theaccompanying drawings. Note that the present invention is not limited tothe following description, and it will be easily understood by thoseskilled in the art that various changes and modifications can be madewithout departing from the spirit and scope of the present invention.Therefore, the present invention should not be construed as beinglimited to the description in the following embodiments. Note that inthe structures of the invention described below, the same portions orportions having similar functions are denoted by the same referencenumerals in different drawings, and description of such portions is notrepeated.

Embodiment 1

In this embodiment, a light-emitting element of one embodiment of thepresent invention will be described with reference to FIGS. 1A to 1D.

A light-emitting element of one embodiment of the present inventionincludes an organic compound having a phenylcarbazole skeleton. Theorganic compound has a high hole-transport property. Thus, when theorganic compound is used for a light-emitting element, a light-emittingelement having high emission efficiency can be obtained. Further, alight-emitting element in which increase of driving voltage issuppressed can be obtained.

One embodiment of the present invention is a light-emitting elementincluding an organic compound between a pair of electrodes. Themolecular weight X of the organic compound is greater than or equal to450 and less than or equal to 1500. The absorption edge of the organiccompound is at 380 nm or more. By LC/MS analysis in a positive mode inwhich an argon gas is made to collide with the organic compoundsubjected to LC separation at any energy higher than or equal to 1 eVand lower than or equal to 30 eV, a product ion is detected at leastaround m/z=(X−240).

In this specification, by analysis of an organic compound included in alight-emitting element by LC/MS, a skeleton of the organic compound inthe light-emitting element can be identified. When the molecular weightof the organic compound included in a light-emitting element of oneembodiment of the present invention is X, a product ion is detected atleast around m/z=(X−240) by LC/MS analysis performed under theabove-described conditions for the organic compound subjected to LCseparation. The product ion which is detected in one embodiment of thepresent invention is derived from a proton adduct of a cation in a statewhere phenylcarbazole skeleton is eliminated from the organic compound,and is one of characteristic product ions representing the organiccompound having the phenylcarbazole skeleton.

Example 5 which is described later shows an example in which a production is detected around m/z=246 by LC/MS analysis in a positive mode inwhich an argon gas is made to collide at an energy of 6 eV with anorganic compound whose molecular weight is 486. Example 5 also shows anexample in which a product ion is detected around m/z=322 by LC/MSanalysis in a positive mode in which an argon gas is made to collide atan energy of 6 eV with an organic compound whose molecular weight is562.

One embodiment of the present invention is a light-emitting elementincluding an organic compound between a pair of electrodes. Themolecular weight of the organic compound is greater than or equal to 450and less than or equal to 1500. The absorption edge of the organiccompound is at 380 nm or more. The organic compound includes aphenylcarbazole skeleton and an N-biphenyl-N-phenylamine skeleton. ByLC/MS analysis in a positive mode in which an argon gas is made tocollide at any energy higher than or equal to 1 eV and lower than orequal to 30 eV with the organic compound subjected to LC separation, aproduct ion of m/z derived from at least the N-biphenyl-N-phenylamineskeleton is detected.

One embodiment of the present invention is a light-emitting elementincluding an organic compound between a pair of electrodes. Themolecular weight of the organic compound is greater than or equal to 450and less than or equal to 1500. The absorption edge of the organiccompound is at 380 nm or more. The organic compound includes aphenylcarbazole skeleton and an N,N-bis-biphenylamine skeleton. By LC/MSanalysis in a positive mode in which an argon gas is made to collide atany energy higher than or equal to 1 eV and lower than or equal to 30 eVwith the organic compound subjected to LC separation, a product ion ofm/z derived from at least the N,N-bis-biphenylamine skeleton isdetected.

A product ion is detected in the light-emitting element of oneembodiment of the present invention and derived from anN-biphenyl-N-phenylamine skeleton or an N,N-bis-biphenylamine skeleton.The product ion is derived from a radical cation in a state from which aphenylcarbazole skeleton is eliminated from the organic compound, and isone of characteristic product ions representing the organic compoundhaving the phenylcarbazole skeleton and the N-biphenyl-N-phenylamineskeleton or the N,N-bis-biphenylamine skeleton.

In each of the above-described structures, a product ion may be detectedat least around m/z=243 in a qualitative spectrum (a positive ion) ofthe organic compound measured with a TOF-SIMS in which Bi₃ ⁺⁺ is used asa primary ion and the amount of irradiation with the primary ion isgreater than or equal to 8×10¹⁰ ions/cm² and less than or equal to1×10¹² ions/cm².

In this specification, by analysis of an organic compound in alight-emitting element with a TOF-SIMS, a skeleton of the organiccompound in the light-emitting element can be identified. A product ionis detected at least around m/z=243 in a qualitative spectrum (apositive ion) of the organic compound included in the light-emittingelement of one embodiment of the present invention which is measuredwith a TOF-SIMS under the above-described conditions. The product iondetected around m/z=243 in one embodiment of the present invention isderived from a proton adduct of a radical cation of phenylcarbazoleskeleton, and is one of characteristic product ions representing theorganic compound having the phenylcarbazole skeleton.

<<Structural Example of Light-Emitting Element>>

A light-emitting element illustrated in FIG. 1A includes an EL layer 203between a first electrode 201 and a second electrode 205. In thisembodiment, the first electrode 201 serves as an anode, and the secondelectrode 205 serves as a cathode.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the first electrode 201 and the secondelectrode 205, holes are injected to the EL layer 203 from the firstelectrode 201 side and electrons are injected to the EL layer 203 fromthe second electrode 205 side. The injected electrons and holes arerecombined in the EL layer 203 and a light-emitting substance containedin the EL layer 203 emits light.

The EL layer 203 includes at least a light-emitting layer containing alight-emitting substance. For the EL layer 203, either a low molecularcompound or a high molecular compound can be used, and an inorganiccompound may also be used.

In addition to the light-emitting layer, the EL layer 203 may furtherinclude one or more layers containing any of a substance with a highhole-injection property, a substance with a high hole-transportproperty, a substance with a high electron-transport property, asubstance with a high electron-injection property, a substance with abipolar property (a substance with a high electron-transport propertyand a high hole-transport property), and the like.

Further, when a plurality of light-emitting layers are provided in theEL layer and emission colors of the layers are made different, lightemission of a desired color can be provided from the light-emittingelement as a whole. For example, in a light-emitting element having twolight-emitting layers, the emission colors of first and secondlight-emitting layers are complementary, so that the light-emittingelement can emit white light as a whole. Note that the word“complementary” means color relationship in which an achromatic color isobtained when colors are mixed. In other words, when lights obtainedfrom substances which emit light of complementary colors are mixed,white emission can be obtained. Further, the same applies to alight-emitting element having three or more light-emitting layers.

A light-emitting element illustrated in FIG. 1B includes the EL layer203 between the first electrode 201 and the second electrode 205, and inthe EL layer 203, a hole-injection layer 301, a hole-transport layer302, the light-emitting layer 303, an electron-transport layer 304, andan electron-injection layer 305 are stacked in that order from the firstelectrode 201 side.

As in light-emitting elements illustrated in FIGS. 1C and 1D, aplurality of EL layers may be stacked between the first electrode 201and the second electrode 205. In this case, an intermediate layer 207 ispreferably provided between the stacked EL layers. The intermediatelayer 207 includes at least a charge-generation region.

For example, the light-emitting element illustrated in FIG. 1C includesthe intermediate layer 207 between a first EL layer 203 a and a secondEL layer 203 b. The light-emitting element illustrated in FIG. 1Dincludes n EL layers (n is a natural number of 2 or more), and theintermediate layers 207 between the EL layers.

The following will show behaviors of electrons and holes in theintermediate layer 207 between the EL layer 203(m) and the EL layer203(m+1). When a voltage higher than the threshold voltage of thelight-emitting element is applied between the first electrode 201 andthe second electrode 205, holes and electrons are generated in theintermediate layer 207, and the holes move into the EL layer 203(m+1)provided on the second electrode 205 side and the electrons move intothe EL layer 203(m) provided on the first electrode 201 side. The holesinjected into the EL layer 203(m+1) are recombined with the electronsinjected from the second electrode 205 side, so that a light-emittingsubstance contained in the EL layer 203(m+1) emits light. Further, theelectrons injected into the EL layer 203(m) are recombined with theholes injected from the first electrode 201 side, so that alight-emitting substance contained in the EL layer 203(m) emits light.Thus, the holes and electrons generated in the intermediate layer 207cause light emission in the respective EL layers.

Note that the EL layers can be provided in contact with each other withno intermediate layer interposed therebetween when these EL layers allowthe same structure as the intermediate layer to be formed therebetween.For example, when the charge-generation region is formed over onesurface of an EL layer, another EL layer can be provided in contact withthe surface.

Further, by forming EL layers to emit light of different colors fromeach other, a light-emitting element as a whole can provide lightemission of a desired color. For example, in a light-emitting elementhaving two EL layers, the emission colors of first and second EL layersare complementary, so that the light-emitting element can emit whitelight as a whole. This can be applied to a light-emitting element havingthree or more EL layers.

<<Organic Compound>>

Next, the organic compound having a phenylcarbazole skeleton which isincluded in the light-emitting element of one embodiment of the presentinvention is described in detail. The organic compound has a highhole-transport property. In the light-emitting element of one embodimentof the present invention, the organic compound is included in at leastany one of a hole-injection layer, a hole-transport layer, and alight-emitting layer. In the case of being included in thelight-emitting layer, the organic compound can be used as alight-emitting substance (guest material) or a host material in which aguest material is dispersed.

As an example the organic compound included in the light-emittingelement of one embodiment of the present invention, an organic compoundrepresented by a general formula (G1) is given.

In the general formula (G1), R¹ represents hydrogen, an alkyl grouphaving 1 to 6 carbon atoms, or a substituted or unsubstituted phenylgroup, R² to R⁶ separately represent hydrogen, an alkyl group having 1to 6 carbon atoms, a substituted or unsubstituted phenyl group, asubstituted or unsubstituted naphthyl group, or a substituted orunsubstituted phenanthryl group, Ar¹ represents hydrogen, a substitutedor unsubstituted phenyl group, a substituted or unsubstituted naphthylgroup, or a substituted or unsubstituted phenanthryl group, and Ar²represents a substituted or unsubstituted phenyl group, a substituted orunsubstituted naphthyl group, or a substituted or unsubstitutedphenanthryl group.

Note that in the case where the phenyl group, the naphthyl group, or thephenanthryl group includes a substituent, an alkyl group having 1 to 6carbon atoms is given as an example of the substituent. A substituent ispreferably included because in that case a bulkier structure can beobtained.

As for R² to R⁶ in the general formula (G1), the following case ispreferable: R⁴ is a substituent other than hydrogen and R², R³, R⁵, andR⁶ are each hydrogen (i.e., a phenylene group having R² to R⁶ is aparaphenylene group). In this case, driving voltage of thelight-emitting element is low. Further, as for R² to R⁶ in the generalformula (G1), the following cases are preferable: a case where R² is asubstituent other than hydrogen and R³, R⁴, R⁵, and R⁶ are eachhydrogen; a case where R³ is a substituent other than hydrogen and R²,R⁴, R⁵, and R⁶ are each hydrogen; and the like (i.e., a case where aphenylene group having R² to R⁶ is a metaphenylene group or anorthophenylene group). In these cases, a band gap of the organiccompound is wide and the level of singlet excitation energy (S₁ level)and the level of triplet excitation energy (T₁ level) are high.

As examples of R¹ in the general formula (G1), structural formulae (s−1)to (s−5) and the like can be given in addition to hydrogen. As examplesof R² to R⁶ in the general formula (G1), structural formulae (s−1) to(s−8) and the like can be given in addition to hydrogen. As examples ofAr¹ in the general formula (G1), structural formulae (s−5) to (s−8) andthe like can be given in addition to hydrogen. As examples of Ar² in thegeneral formula (G1), structural formulae (s−5) to (s−8) and the likecan be given in addition to hydrogen.

Note that an alkyl group which is represented by any of the structuralformulae (s−1) to (s−4) is preferably used because, in that case, ahigher amorphous property of the organic compound can be obtained. Theuse of such an alkyl group is preferable also because favorablesolubility of the organic compound in an organic solvent can beachieved, which facilitates purification and solution preparation.Further, a phenyl group which is represented by the structural formula(s−5) is preferably used because, in that case, the band gap of theorganic compound is wide and the S₁ level and the T₁ level are high. Anaryl group which is represented by any of the structural formulae (s−5)to (s−8) is preferably used because, in that case, the carrier-transportproperty of the organic compound can be improved. A condensed ring ispreferably included as shown in any of the structural formulae (s−6) to(s−8) because, in that case, the carrier-transport property of theorganic compound can be further improved.

As an example of the organic compound included in the light-emittingelement of one embodiment of the present invention, an organic compoundrepresented by a general formula (G2) is given.

In the general formula (G2), R² to R⁶ separately represent hydrogen, analkyl group having 1 to 6 carbon atoms, a substituted or unsubstitutedphenyl group, a substituted or unsubstituted naphthyl group, or asubstituted or unsubstituted phenanthryl group, Ar¹ represents hydrogen,a substituted or unsubstituted phenyl group, a substituted orunsubstituted naphthyl group, or a substituted or unsubstitutedphenanthryl group, and Ar² represents a substituted or unsubstitutedphenyl group, a substituted or unsubstituted naphthyl group, or asubstituted or unsubstituted phenanthryl group.

As specific examples of R² to R⁶, Ar¹, and Ar² in the general formula(G2), examples similar to those for the general formula (G1) can begiven.

As an example of the organic compound included in the light-emittingelement of one embodiment of the present invention, an organic compoundrepresented by a general formula (G3) is given.

In the general formula (G3), Ar¹ represents hydrogen, a substituted orunsubstituted phenyl group, a substituted or unsubstituted naphthylgroup, or a substituted or unsubstituted phenanthryl group, and Ar²represents a substituted or unsubstituted phenyl group, a substituted orunsubstituted naphthyl group, or a substituted or unsubstitutedphenanthryl group.

As specific examples of Ar¹ and Ar² in the general formula (G3),examples similar to those for the general formula (G1) can be given.

As an example of the organic compound included in the light-emittingelement of one embodiment of the present invention, an organic compoundrepresented by a general formula (G4) is given.

In the general formula (G4), Ar¹ represents hydrogen, a substituted orunsubstituted phenyl group, a substituted or unsubstituted naphthylgroup, or a substituted or unsubstituted phenanthryl group, and Ar²represents a substituted or unsubstituted phenyl group, a substituted orunsubstituted naphthyl group, or a substituted or unsubstitutedphenanthryl group.

As specific examples of Ar¹ and Ar² in the general formula (G4),examples similar to those for the general formula (G1) can be given.

Note that in any of the general formulae (G1) to (G4), one or more alkylgroups each having 1 to 6 carbon atoms (e.g., a methyl group, an ethylgroup, a tert-butyl group, or a cyclohexyl group), one or more phenylgroups, or one or more biphenyl groups may be further bonded.

By analysis of the organic compound represented by any of the generalformulae (G1) to (G4) by LC/MS, a skeleton of the organic compound inthe light-emitting element can be identified.

For example, in the organic compound represented by the general formula(G1), a product ion derived from at least one of structures representedby general formulae (P1-1) to (P1-10) (or structures showing the same orsubstantially the same m/z values as the structures represented by thegeneral formulae (P1-1) to (P1-10)) is detected. It is likely that,particularly, a product ion derived from the structure represented bythe general formula (P1-1) (or a structure showing the same orsubstantially the same m/z value as the structure represented by thegeneral formula (P1-1)) is easily detected.

For example, in the organic compound represented by the general formula(G2), a product ion derived from at least one of structures representedby general formulae (P2-1) to (P2-10) (or structures showing the same orsubstantially the same m/z values as the structures represented by thegeneral formulae (P2-1) to (P2-10)) is detected. It is likely that,particularly, a product ion derived from the structure represented bythe general formula (P2-1) (or a structure showing the same orsubstantially the same m/z value as the structure represented by thegeneral formula (P2-1)) is easily detected.

For example, in the organic compound represented by the general formula(G3), a product ion derived from at least one of structures representedby general formulae (P3-1) to (P3-10) (or structures showing the same orsubstantially the same m/z values as the structures represented by thegeneral formulae (P3-1) to (P3-10)) is detected. It is likely that,particularly, a product ion derived from the structure represented bythe general formula (P3-1) (or a structure showing the same orsubstantially the same m/z value as the structure represented by thegeneral formula (P3-1)) is easily detected.

For example, in the organic compound represented by the general formula(G4), a product ion derived from at least one of structures representedby general formulae (P4-1) to (P4-10) (or structures showing the same orsubstantially the same m/z values as the structures represented by thegeneral formulae (P4-1) to (P4-10)) is detected. It is likely that,particularly, a product ion derived from the structure represented bythe general formula (P4-1) (or a structure showing the same orsubstantially the same in/z value as the structure represented by thegeneral formula (P4-1)) is easily detected.

Specific examples of the structural formula of the above-describedorganic compound are structural formulae (100) to (116) given below.Note that the present invention is not limited to these formulae.

Next, an example of a method for synthesizing the organic compoundrepresented by the general formula (G1) is described.

The organic compound represented by the general formula (G1) is obtainedby coupling of a carbazole compound (a1) having a halogen group (X¹) anda diarylamine derivative (a2) as shown in a synthesis scheme (A).

Note that the coupling reaction of the carbazole compound (a1) having ahalogen group and the diarylamine derivative (a2) which is shown in thesynthesis scheme (A) can be performed by a variety of methods and any ofthem is applicable; here, the case where the Buchwald-Hartwig reactionis used is described as an example.

A palladium catalyst can be used as a metal catalyst, and a mixture of apalladium complex and a ligand thereof can be used as a palladiumcatalyst. As examples of the palladium complex,bis(dibenzylideneacetone)palladium(0), palladium(II) acetate, and thelike can be given. As the ligand, tri(tert-butyl)phosphine,tri(n-hexyl)phosphine, tricyclohexylphosphine,1,1-bis(diphenylphosphino)ferrocene (abbreviation: DPPF), and the likecan be given. As a substance which can be used as a base, an organicbase such as sodium tert-butoxide, an inorganic base such as potassiumcarbonate, and the like can be given. In addition, the above reaction ispreferably performed in a solution, and toluene, xylene, benzene, andthe like can be given as a solvent that can be used in the abovereaction. However, the catalyst, ligand, base, and solvent which can beused are not limited thereto. In addition, the reaction is morepreferably performed under an inert atmosphere of nitrogen, argon, orthe like.

Although examples of the synthesis methods are described above, theorganic compound included in the light-emitting element of oneembodiment of the present invention may be synthesized by any othersynthesis method.

<<Materials of Light-Emitting Element>>

Examples of materials which can be used for layers which form thelight-emitting element will be described below. Note that each layer isnot limited to a single layer, and may be a stack of two or more layers.

<Anode>

The electrode serving as the anode (the first electrode 201 in thisembodiment) can be formed using one or more kinds of conductive metals,alloys, conductive compounds, and the like. In particular, it ispreferable to use a material with a high work function (4.0 eV or more).Examples include indium tin oxide (ITO), indium tin oxide containingsilicon or silicon oxide, indium zinc oxide, indium oxide containingtungsten oxide and zinc oxide, graphene, gold, platinum, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, palladium,titanium, and a nitride of a metal material (e.g., titanium nitride).

When the anode is in contact with the charge-generation region, any of avariety of conductive materials can be used regardless of their workfunctions; for example, aluminum, silver, an alloy containing aluminum,or the like can be used.

<Cathode>

The electrode serving as the cathode (the second electrode 205 in thisembodiment) can be formed using one or more kinds of conductive metals,alloys, conductive compounds, and the like. In particular, it ispreferable to use a material with a low work function (3.8 eV or less).Examples include aluminum, silver, an element belonging to Group 1 or 2of the periodic table (e.g., an alkali metal such as lithium or cesium,an alkaline earth metal such as calcium or strontium, or magnesium), analloy containing any of these elements (e.g., Mg—Ag or Al—Li), a rareearth metal such as europium or ytterbium, and an alloy containing anyof these rare earth metals.

Note that when the cathode is in contact with the charge-generationregion, a variety of conductive materials can be used regardless of itswork function. For example, ITO, silicon, or indium tin oxide containingsilicon oxide can be used.

The electrodes may be formed separately by a vacuum evaporation methodor a sputtering method. Alternatively, when a silver paste or the likeis used, a coating method or an inkjet method may be used.

<Light-Emitting Layer>

As described above, the light-emitting element of this embodimentincludes the light-emitting substance (guest material) in thelight-emitting layer 303. As the guest material, a fluorescent compound,a phosphorescent compound, a substance exhibiting thermally activateddelayed fluorescence, or the like can be used. Further, thelight-emitting layer 303 may include another compound (host material orthe like) in addition to the guest material.

Examples of the fluorescent compound that can be used for thelight-emitting layer include the organic compounds represented by theabove general formulae (G1) to (G4),N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-N,N′-diphenyl-pyrene-1,6-diamine(abbreviation: 1,6FLPAPrn),N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA), perylene, 2,5,8,11-tetra-tert-butylperylene(abbreviation: TBP),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine] (abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA),N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), coumarin 30,N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCABPhA),N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPABPhA),9,10-bis(1,1′-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine(abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine(abbreviation: DPhAPhA), coumarin 545T, N,N′-diphenylquinacridone(abbreviation: DPQd), rubrene,5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT),2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile(abbreviation: DCM1),2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCM2),N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation:p-mPhTD),7,14-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-α]fluoranthene-3,10-diamine(abbreviation: p-mPhAFD),2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTI),2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTB),2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile(abbreviation: BisDCM), and2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: BisDCJTM).

Examples of the phosphorescent compound that can be used for thelight-emitting layer includebis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III) picolinate(abbreviation: FIrpic),bis[2-(3′,5′-bistrifluoromethylphenyl)pyridinato-N,C^(2′)]iridium(III)picolinate(abbreviation: [Ir(CF₃ppy)₂(pic)]),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIracac),tris(2-phenylpyridinato)iridium(III) (abbreviation: [Ir(ppy)₃]),bis(2-phenylpyridinato)iridium(III) acetylacetonate (abbreviation:[Ir(ppy)₂(acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate(abbreviation: [Ir(bzq)₂(acac)]),bis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(dpo)₂(acac)]),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C^(2′)}iridium(III)acetylacetonate (abbreviation: [Ir(p-PF-ph)₂(acac)]),bis(2-phenylbenzothiazolato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: [Ir(bt)₂(acac)]),bis[2-(2′-benzo[4,5-α]thienyl)pyridinato-N,C^(3′)]iridium(III)(acetylacetonate)(abbreviation: [Ir(btp)₂(acac)]),bis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: [Ir(piq)₂(acac)]),(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]),(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphineplatinum(II)(abbreviation: PtOEP), tris(acetylacetonato) (monophenanthroline)terbium(III) (abbreviation: Tb(acac)₃(Phen)),tris(1,3-diphenyl-1,3-propanedionato) (monophenanthroline)europium(III)(abbreviation: Eu(DBM)₃(Phen)),tris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: Eu(TTA)₃(Phen)), andbis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]).

The guest material is preferably dispersed in the host material. Whenthe light-emitting layer has the structure in which the guest materialis dispersed in the host material, the crystallization of thelight-emitting layer can be inhibited. Further, it is possible tosuppress concentration quenching due to high concentration of the guestmaterial, and thus the light-emitting element can have higher emissionefficiency. A compound to be described below which easily acceptselectrons or a compound to be described below which easily accepts holescan be used as the host material. For example, the organic compoundsrepresented by the general formulae (G1) to (G4) may be used for thehost material in the case where the guest material is a fluorescentcompound or a phosphorescent compound exhibiting emission of light witha wavelength longer than or equal to that of yellow light.

Note that the T₁ level of the host material (or a material other thanthe guest material in the light-emitting layer) is preferably higherthan the T₁ level of the guest material. This is because, when the T₁level of the host material is lower than the T₁ level of the guestmaterial, the triplet excitation energy of the guest material which isto contribute to light emission is quenched by the host material andaccordingly the emission efficiency is decreased.

Here, for improvement in efficiency of energy transfer from a hostmaterial to a guest material, Førster mechanism (dipole-dipoleinteraction) and Dexter mechanism (electron exchange interaction), whichare known as mechanisms of energy transfer between molecules, areconsidered. According to the mechanisms, it is preferable that anemission spectrum of a host material (fluorescence spectrum in energytransfer from a singlet excited state, phosphorescence spectrum inenergy transfer from a triplet excited state) largely overlap with anabsorption spectrum of a guest material (specifically, spectrum in anabsorption band on the longest wavelength (lowest energy) side).

However, in general, it is difficult to obtain an overlap between afluorescence spectrum of a host material and an absorption spectrum inan absorption band on the longest wavelength (lowest energy) side of aguest material. The reason for this is as follows: if the fluorescencespectrum of the host material overlaps with the absorption spectrum inthe absorption band on the longest wavelength (lowest energy) side ofthe guest material, since a phosphorescence spectrum of the hostmaterial is located on a longer wavelength (lower energy) side ascompared to the fluorescence spectrum, the T₁ level of the host materialbecomes lower than the T₁ level of the phosphorescent compound and theabove-described problem of quenching occurs; yet, when the host materialis designed in such a manner that the T₁ level of the host material ishigher than the T₁ level of the phosphorescent compound to avoid theproblem of quenching, the fluorescence spectrum of the host material isshifted to the shorter wavelength (higher energy) side, and thus thefluorescence spectrum does not have any overlap with the absorptionspectrum in the absorption band on the longest wavelength (lowestenergy) side of the guest material. For that reason, in general, it isdifficult to obtain an overlap between a fluorescence spectrum of a hostmaterial and an absorption spectrum in an absorption band on the longestwavelength (lowest energy) side of a guest material so as to maximizeenergy transfer from a singlet excited state of a host material.

Thus, it is preferable that in a light-emitting layer of alight-emitting element of one embodiment of the present invention whichuses a phosphorescent compound as a guest material, a third substance becontained in addition to the phosphorescent compound and the hostmaterial (which are respectively regarded as a first substance and asecond substance contained in the light-emitting layer), and acombination of the host material the third substance form an exciplex(also referred to as excited complex). In that case, the host materialand the third substance form an exciplex at the time of recombination ofcarriers (electrons and holes) in the light-emitting layer. Thus, in thelight-emitting layer, fluorescence spectra of the host material and thethird substance are converted into an emission spectrum of the exciplexwhich is located on a longer wavelength side. Moreover, when the hostmaterial and the third substance are selected such that the emissionspectrum of the exciplex has a large overlap with the absorptionspectrum of the guest material, the efficiency of energy transfer from asinglet excited state can be maximized. Note that also in the case of atriplet excited state, energy transfer from the exciplex, not the hostmaterial, is assumed to occur. In one embodiment of the presentinvention to which such a structure is applied, energy transferefficiency can be improved owing to energy transfer utilizing an overlapbetween an emission spectrum of an exciplex and an absorption spectrumof a phosphorescent compound; accordingly, a light-emitting element withhigh external quantum efficiency can be provided.

As the guest material, a phosphorescent compound described above or thelike can be used. Although any combination of the host material and thethird substance can be used as long as an exciplex is formed, a compoundwhich easily accepts electrons (a compound having an electron-trappingproperty) and a compound which easily accepts holes (a compound having ahole-trapping property) are preferably combined.

Examples of a compound which easily accepts holes and which can be usedas the host material or the third substance include the organiccompounds represented by the general formulae (G1) to (G4), a π-electronrich heteroaromatic compound (e.g., a carbazole derivative or an indolederivative) and an aromatic amine compound.

Specifically, the following examples can be given:4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1),4,4′,4″-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation:1′-TNATA),2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9′-bifluorene(abbreviation: DPA2SF),N,N′-bis(9-phenylcarbazol-3-yl)-N,N′-diphenylbenzene-1,3-diamine(abbreviation: PCA2B),N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine(abbreviation: DPNF),N,N′,N″-triphenyl-N,N′,N″-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine(abbreviation: PCA3B),2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: PCASF),2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: DPASF),N,N′-bis[4-(carbazol-9-yl)phenyl]-N,N′-diphenyl-9,9-dimethylfluorene-2,7-diamine(abbreviation: YGA2F),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N′-phenyl-N′-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine(abbreviation: DFLADFL),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1), 3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA1),3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA2),4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl(abbreviation: DNTPD), and3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole(abbreviation: PCzTPN2).

The following examples can also be given: aromatic amine compounds suchas 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation:TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), and4,4′-bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: DFLDPBi); and carbazole derivatives such as4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA),and 9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: PCzPA). In addition, high molecular compounds such aspoly(N-vinylcarbazole) (abbreviation: PVK), poly(4-vinyltriphenylamine)(abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), andpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can be given.

Examples of the compound which easily accepts electrons and which can beused as the host material or the third substance include a π-electrondeficient heteroaromatic compound such as a nitrogen-containingheteroaromatic compound, a metal complex having a quinoline skeleton ora benzoquinoline skeleton, and a metal complex having an oxazole-basedligand or a thiazole-based ligand.

Specific examples include the following: metal complexes such asbis(10-hydroxybenzo[h]quinolinato)berylium(II) (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato) (4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-hydroxyphenyl)benzoxazolato]zinc (abbreviation: Zn(BOX)₂), andbis[2-(2-hydroxyphenyl)benzothiazolato]zinc(II) (abbreviation:Zn(BTZ)₂); heterocyclic compounds having polyazole skeletons, such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), and2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II); heterocyclic compounds having quinoxalineskeletons or dibenzoquinoxaline skeletons, such as2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:2mDBTPDBq-II), 2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTBPDBq-II),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 2CzPDBq-III),7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), 6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 6mDBTPDBq-II), and2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mCzBPDBq); heterocyclic compounds having diazineskeletons (pyrimidine skeletons or pyrazine skeletons), such as4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation:4,6mPnP2Pm), 4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine(abbreviation: 4,6mCzP2Pm), and4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II); heterocyclic compounds having pyridine skeletons, suchas 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation: 35DCzPPy),1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB), and3,3′,5,5′-tetra[(m-pyridyl)-phen-3-yl]biphenyl (abbreviation: BP4mPy).Among the above-described compounds, the heterocyclic compounds havingquinoxaline skeletons or dibenzoquinoxaline skeletons, the heterocycliccompounds having diazine skeletons, and the heterocyclic compoundshaving pyridine skeletons have favorable reliability and can preferablybe used.

The following examples can also be given: metal complexes havingquinoline skeletons or benzoquinoline skeletons, such astris(8-quinolinolato)aluminum(III) (abbreviation: Alq) andtris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃); andheteroaromatic compounds such as bathophenanthroline (abbreviation:BPhen), bathocuproine (abbreviation: BCP),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), and 4,4′-bis(5-methylbenzoxazol-2-yl)stilbene(abbreviation: BzOs). In addition, high molecular compounds such aspoly(2,5-pyridinediyl) (abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py) andpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can also be given.

The materials which can be used as the host material or the thirdsubstance are not limited to the above materials as long as acombination of the material used as the host material and the materialused as the third substance can form an exciplex, an emission spectrumof the exciplex overlaps with an absorption spectrum of the guestmaterial, and a peak of the emission spectrum of the exciplex is locatedon a longer wavelength side than a peak of the absorption spectrum ofthe guest material.

Note that when a compound which easily accepts electrons and a compoundwhich easily accepts holes are used for the host material and the thirdsubstance, carrier balance can be controlled by the mixture ratio of thecompounds. Specifically, the ratio of the host material to the thirdsubstance is preferably from 1:9 to 9:1.

Further, the exciplex may be formed at the interface between two layers.For example, when a layer containing the compound which easily acceptselectrons and a layer containing the compound which easily accepts holesare stacked, the exciplex is formed in the vicinity of the interfacethereof. These two layers may be used as the light-emitting layer in thelight-emitting element of one embodiment of the present invention. Inthat case, the phosphorescent compound may be added to the vicinity ofthe interface. The phosphorescent compound may be added to one of thetwo layers or both.

<Hole-Transport Layer>

The hole-transport layer 302 contains a substance with a highhole-transport property.

The substance with a high hole-transport property is preferably asubstance with a property of transporting more holes than electrons, andis especially preferably a substance with a hole mobility of 10⁻⁶ cm²/Vsor more.

For the hole-transport layer 302, it is possible to use any of thecompounds which easily accept holes and are described, e.g., the organiccompounds represented by the general formulae (G1) to (G4), as examplesof the substance applicable to the light-emitting layer 303.

It is also possible to use an aromatic hydrocarbon compound such as2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),9,10-di(2-naphthyl)anthracene (abbreviation: DNA), or9,10-diphenylanthracene (abbreviation: DPAnth).

<Electron-Transport Layer>

The electron-transport layer 304 contains a substance with a highelectron-transport property.

The substance with a high electron-transport property is preferably anorganic compound having a property of transporting more electrons thanholes, and is especially preferably a substance with an electronmobility of 10⁻⁶ cm²/Vs or more.

For the electron-transport layer 304, it is possible to use any of thecompounds which easily accept electrons and are described as examples ofthe substance applicable to the light-emitting layer 303.

<Hole-Injection Layer>

The hole-injection layer 301 contains a substance with a highhole-injection property.

Examples of the substance with a high hole-injection property includemetal oxides such as molybdenum oxide, titanium oxide, vanadium oxide,rhenium oxide, ruthenium oxide, chromium oxide, zirconium oxide, hafniumoxide, tantalum oxide, silver oxide, tungsten oxide, and manganeseoxide.

A phthalocyanine-based compound such as phthalocyanine (abbreviation:H₂Pc), or copper(II) phthalocyanine (abbreviation: CuPc) can also beused.

Further alternatively, it is possible to use an aromatic amine compoundwhich is a low molecular organic compound, such as TDATA, MTDATA, DPAB,DNTPD, 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B), PCzPCA1, PCzPCA2, or PCzPCN1.

Further alternatively, it is possible to use a high molecular compoundsuch as PVK, PVTPA, PTPDMA, or Poly-TPD, or a high molecular compound towhich acid is added, such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)(abbreviation: PEDOT/PSS) or polyaniline/poly(styrenesulfonic acid)(abbreviation: PAni/PSS).

The hole-injection layer 301 may serve as the charge-generation region.When the hole-injection layer 301 in contact with the anode serves asthe charge-generation region, a variety of conductive materials can beused for the anode regardless of their work functions. Materialscontained in the charge-generation region will be described later.

<Electron-Injection Layer>

The electron-injection layer 305 contains a substance with a highelectron-injection property.

Examples of the substance with a high electron-injection propertyinclude an alkali metal, an alkaline earth metal, a rare earth metal,and a compound thereof (e.g., an oxide thereof, a carbonate thereof, anda halide thereof), such as lithium, cesium, calcium, lithium oxide,lithium carbonate, cesium carbonate, lithium fluoride, cesium fluoride,calcium fluoride, and erbium fluoride.

The electron-injection layer 305 may serve as the charge-generationregion. When the electron-injection layer 305 in contact with thecathode serves as the charge-generation region, any of a variety ofconductive materials can be used for the cathode regardless of theirwork functions. Materials contained in the charge-generation region willbe described later.

<Charge-Generation Region>

The charge-generation region may have either a structure in which anelectron acceptor (acceptor) is added to an organic compound with a highhole-transport property or a structure in which an electron donor(donor) is added to an organic compound with a high electron-transportproperty. Alternatively, these structures may be stacked.

As examples of an organic compound with a high hole-transport property,the above materials which can be used for the hole-transport layer,e.g., the organic compounds represented by the above general formulae(G1) to (G4), can be given, and as examples of an organic compound witha high electron-transport property, the above materials which can beused for the electron-transport layer can be given.

Further, as examples of the electron acceptor, 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ),chloranil, and the like can be given. In addition, a transition metaloxide can be given. In addition, an oxide of metals that belong to Group4 to Group 8 of the periodic table can be given. Specifically, vanadiumoxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide,tungsten oxide, manganese oxide, and rhenium oxide are preferable sincetheir electron-accepting property is high. Among these, molybdenum oxideis especially preferable because it is stable in the air, has a lowhygroscopic property, and is easily handled.

Further, as the electron donor, it is possible to use an alkali metal,an alkaline earth metal, a rare earth metal, a metal belonging to Group2 or Group 13 of the periodic table, or an oxide or a carbonate thereof.Specifically, lithium, cesium, magnesium, calcium, ytterbium, indium,lithium oxide, cesium carbonate, or the like is preferably used.Alternatively, an organic compound such as tetrathianaphthacene may beused as the electron donor.

The above-described layers included in the EL layer 203 and theintermediate layer 207 can be formed separately by any of the followingmethods: an evaporation method (including a vacuum evaporation method),a transfer method, a printing method, an inkjet method, a coatingmethod, and the like.

By use of the light-emitting element described in this embodiment, apassive matrix light-emitting device or an active matrix light-emittingdevice in which driving of the light-emitting element is controlled by atransistor can be manufactured. Furthermore, the light-emitting devicecan be applied to an electronic device, a lighting device, or the like.

As described above, a light-emitting element of one embodiment of thepresent invention includes an organic compound having a phenylcarbazoleskeleton. Since the organic compound has a high hole-transport property,low voltage driving and high efficiency of a light-emitting element canbe achieved. Further, by performing LC/MS analysis or TOF-SIMS analysison the organic compound included in thelight-emitting element of oneembodiment of the present invention, a skeleton of the organic compoundcan be identified. Specifically, by performing LC/MS analysis orTOF-SIMS analysis on the organic compound, a characteristic product ionrepresenting the organic compound having the phenylcarbazole skeletoncan be detected.

This embodiment can be freely combined with other embodiments.

Embodiment 2

In this embodiment, a light-emitting device of one embodiment of thepresent invention will be described with reference to FIGS. 2A and 2Band FIGS. 3A to 3C. The light-emitting device of this embodimentincludes the light-emitting element of one embodiment of the presentinvention. Since the light-emitting element has high emissionefficiency, a light-emitting device with low power consumption can beprovided.

FIG. 2A is a plan view of a light-emitting device of one embodiment ofthe present invention, and FIG. 2B is a cross-sectional view taken alongdashed-dotted line A-B in FIG. 2A.

In the light-emitting device of this embodiment, a light-emittingelement 403 is included in a space 415 surrounded by a support substrate401, a sealing substrate 405, and a sealing material 407. Thelight-emitting element 403 is a light-emitting element having abottom-emission structure; specifically, a first electrode 421 whichtransmits visible light is provided over the support substrate 401, anEL layer 423 is provided over the first electrode 421, and a secondelectrode 425 which reflects visible light is provided over the EL layer423. The light-emitting element 403 is a light-emitting element to whichone embodiment of the present invention in Embodiment 1 is applied.

A first terminal 409 a is electrically connected to an auxiliary wiring417 and the first electrode 421. An insulating layer 419 is providedover the first electrode 421 in a region which overlaps with theauxiliary wiring 417. The first terminal 409 a is electrically insulatedfrom the second electrode 425 by the insulating layer 419. A secondterminal 409 b is electrically connected to the second electrode 425.Note that although the first electrode 421 is formed over the auxiliarywiring 417 in this embodiment, the auxiliary wiring 417 may be formedover the first electrode 421.

A light extraction structure 411 a is preferably provided at theinterface between the support substrate 401 and the atmosphere. Whenprovided at the interface between the support substrate 401 and theatmosphere, the light extraction structure 411 a can reduce light whichcannot be extracted to the atmosphere due to total reflection, resultingin an increase in the light extraction efficiency of the light-emittingdevice.

In addition, a light extraction structure 411 b is preferably providedat the interface between the light-emitting element 403 and the supportsubstrate 401. When the light extraction structure 411 b has unevenness,a planarization layer 413 is preferably provided between the lightextraction structure 411 b and the first electrode 421. Accordingly, thefirst electrode 421 can be a flat film, and generation of leakagecurrent in the EL layer 423 due to the unevenness of the first electrode421 can be prevented. Further, because of the light extraction structure411 b at the interface between the planarization layer 413 and thesupport substrate 401, light which cannot be extracted to the atmospheredue to total reflection can be reduced, so that the light extractionefficiency of the light-emitting device can be increased.

As a material of the light extraction structure 411 a and the lightextraction structure 411 b, a resin can be used, for example.Alternatively, for the light extraction structure 411 a and the lightextraction structure 411 b, a hemispherical lens, a micro lens array, afilm provided with an uneven surface structure, a light diffusing film,or the like can be used. For example, the light extraction structure 411a and the light extraction structure 411 b can be formed by attachingthe lens or film to the support substrate 401 with an adhesive or thelike which has substantially the same refractive index as the supportsubstrate 401 or the lens or film.

The surface of the planarization layer 413 which is in contact with thefirst electrode 421 is flatter than the surface of the planarizationlayer 413 which is in contact with the light extraction structure 411 b.As a material of the planarization layer 413, glass, liquid, a resin, orthe like having a light-transmitting property and a high refractiveindex can be used.

FIG. 3A is a plan view of a light-emitting device of one embodiment ofthe present invention, FIG. 3B is a cross-sectional view taken alongdashed-dotted line C-D in FIG. 3A, and FIG. 3C is a cross-sectional viewillustrating a modified example of the light-emitting portion.

An active matrix light-emitting device of this embodiment includes, overa support substrate 501, a light-emitting portion 551 (the cross sectionof which is illustrated in FIG. 3B and FIG. 3C as a light-emittingportion 551 a and a light-emitting portion 551 b, respectively), adriver circuit portion 552 (gate side driver circuit portion), a drivercircuit portion 553 (source side driver circuit portion), and a sealingmaterial 507. The light-emitting portion 551 and the driver circuitportions 552 and 553 are sealed in a space 515 surrounded by the supportsubstrate 501, a sealing substrate 505, and the sealing material 507.

Any of a separate coloring method, a color filter method, and a colorconversion method can be applied to the light-emitting element of oneembodiment of the present invention. The light-emitting portion 551 afabricated by a color filter method is illustrated in FIG. 3B, and thelight-emitting portion 551 b fabricated by a separate coloring method isillustrated in FIG. 3C.

Each of the light-emitting portion 551 a and the light-emitting portion551 b includes a plurality of light-emitting units each including aswitching transistor 541 a, a current control transistor 541 b, and asecond electrode 525 electrically connected to a wiring (a sourceelectrode or a drain electrode) of the transistor 541 b.

A light-emitting element 503 included in the light-emitting portion 551a has a bottom-emission structure and includes a first electrode 521which transmits visible light, an EL layer 523, and the second electrode525. Further, a partition 519 is formed so as to cover an end portion ofthe first electrode 521.

A light-emitting element 504 included in the light-emitting portion 551b has a top-emission structure and includes a first electrode 561, an ELlayer 563, and the second electrode 565 which transmits visible light.Further, the partition 519 is formed so as to cover an end portion ofthe first electrode 561. In the EL layer 563, at least layers (e.g.,light-emitting layers) which contain a variable material depending onthe light-emitting element are colored separately.

Over the support substrate 501, a lead wiring 517 for connecting anexternal input terminal through which a signal (e.g., a video signal, aclock signal, a start signal, or a reset signal) or a potential from theoutside is transmitted to the driver circuit portion 552 or 553 isprovided. Here, an example is described in which a flexible printedcircuit (FPC) 509 is provided as the external input terminal.

The driver circuit portions 552 and 553 include a plurality oftransistors. FIG. 3B illustrates two of the transistors in the drivercircuit portion 552 (transistors 542 and 543).

To prevent an increase in the number of manufacturing steps, the leadwiring 517 is preferably formed using the same material and the samestep(s) as those of the electrode or the wiring in the light-emittingportion or the driver circuit portion. Described in this embodiment isan example in which the lead wiring 517 is formed using the samematerial and the same step(s) as those of the source electrodes and thedrain electrodes of the transistors included in the light-emittingportion 551 and the driver circuit portion 552.

In FIG. 3B, the sealing material 507 is in contact with a firstinsulating layer 511 over the lead wiring 517. The adhesion of thesealing material 507 to metal is low in some cases. Therefore, thesealing material 507 is preferably in contact with an inorganicinsulating film over the lead wiring 517. Such a structure enables alight-emitting device to have high sealing capability, high adhesion,and high reliability. Examples of the inorganic insulating film includeoxide films of metals and semiconductors, nitride films of metals andsemiconductors, and oxynitride films of metals and semiconductors, andspecifically, a silicon oxide film, a silicon nitride film, a siliconoxynitride film, a silicon nitride oxide film, an aluminum oxide film, atitanium oxide film, and the like.

The first insulating layer 511 has an effect of preventing diffusion ofimpurities into a semiconductor included in the transistor. As thesecond insulating layer 513, an insulating film having a planarizationfunction is preferably selected in order to reduce surface unevennessdue to the transistor.

There is no particular limitation on the structure and materials of thetransistor used in the light-emitting device of one embodiment of thepresent invention. A top-gate transistor may be used, or a bottom-gatetransistor such as an inverted staggered transistor may be used. Thetransistor may be a channel-etched transistor or a channel-protectivetransistor. An n-channel transistor may be used and a p-channeltransistor may also be used.

A semiconductor layer can be formed using silicon or an oxidesemiconductor such as an In—Ga—Zn-based metal oxide.

The sealing substrate 505 illustrated in FIG. 3B is provided with acolor filter 533 as a coloring layer at a position overlapping with thelight-emitting element 503 (a light-emitting region thereof), and isalso provided with a black matrix 531 at a position overlapping with thepartition 519. Further, an overcoat layer 535 is provided so as to coverthe color filter 533 and the black matrix 531. The sealing substrate 505illustrated in FIG. 3C is provided with a desiccant 506.

This embodiment can be combined with any of the other embodiments asappropriate.

Embodiment 3

In this embodiment, examples of electronic devices and lighting devicesto which the light-emitting device of one embodiment of the presentinvention is applied will be described with reference to FIGS. 4A to 4Eand FIGS. 5A and 5B.

Electronic devices of this embodiment each include the light-emittingdevice of one embodiment of the present invention in a display portion.Lighting devices of this embodiment each include the light-emittingdevice of one embodiment of the present invention in a light-emittingportion (lighting portion). An electronic device and a lighting devicewith low power consumption can be provided by adopting thelight-emitting device of one embodiment of the present invention.

Examples of electronic devices to which the light-emitting device isapplied are television devices (also referred to as TV or televisionreceivers), monitors for computers and the like, cameras such as digitalcameras and digital video cameras, digital photo frames, cellular phones(also referred to as portable telephone devices), portable gamemachines, portable information terminals, audio playback devices, largegame machines such as pin-ball machines, and the like. Specific examplesof these electronic devices and lighting devices are illustrated inFIGS. 4A to 4E and FIGS. 5A and 5B.

FIG. 4A illustrates an example of a television device. In a televisiondevice 7100, a display portion 7102 is incorporated in a housing 7101.The display portion 7102 is capable of displaying images. Thelight-emitting device of one embodiment of the present invention can beused for the display portion 7102. In addition, here, the housing 7101is supported by a stand 7103.

The television device 7100 can be operated with an operation switchprovided for the housing 7101 or a separate remote controller 7111. Withoperation keys of the remote controller 7111, channels and volume can becontrolled and images displayed on the display portion 7102 can becontrolled. The remote controller 7111 may be provided with a displayportion for displaying data output from the remote controller 7111.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the use of the receiver, general televisionbroadcasting can be received. Moreover, when the television device isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 4B illustrates an example of a computer. A computer 7200 includes amain body 7201, a housing 7202, a display portion 7203, a keyboard 7204,an external connection port 7205, a pointing device 7206, and the like.Note that this computer is manufactured by using the light-emittingdevice of one embodiment of the present invention for the displayportion 7203.

FIG. 4C illustrates an example of a portable game machine. A portablegame machine 7300 has two housings, a housing 7301 a and a housing 7301b, which are connected with a joint portion 7302 so that the portablegame machine can be opened or closed. The housing 7301 a incorporates adisplay portion 7303 a, and the housing 7301 b incorporates a displayportion 7303 b. In addition, the portable game machine illustrated inFIG. 4C includes a speaker portion 7304, a recording medium insertionportion 7305, an operation key 7306, a connection terminal 7307, asensor 7308 (a sensor having a function of measuring or sensing force,displacement, position, speed, acceleration, angular velocity,rotational frequency, distance, light, liquid, magnetism, temperature,chemical substance, sound, time, hardness, electric field, electriccurrent, voltage, electric power, radiation, flow rate, humidity,gradient, oscillation, odor, or infrared rays), an LED lamp, amicrophone, and the like. It is needless to say that the structure ofthe portable game machine is not limited to the above structure as longas the light-emitting device of one embodiment of the present inventionis used for at least either the display portion 7303 a or the displayportion 7303 b, or both, and may include other accessories asappropriate. The portable game machine illustrated in FIG. 4C has afunction of reading out a program or data stored in a recoding medium todisplay it on the display portion, and a function of sharing informationwith another portable game machine by wireless communication. Note thatfunctions of the portable game machine illustrated in FIG. 4C are notlimited to them, and the portable game machine can have variousfunctions.

FIG. 4D illustrates an example of a cellular phone. A cellular phone7400 is provided with a display portion 7402 incorporated in a housing7401, an operation button 7403, an external connection port 7404, aspeaker 7405, a microphone 7406, and the like. Note that the cellularphone 7400 is manufactured by using the light-emitting device of oneembodiment of the present invention for the display portion 7402.

When the display portion 7402 of the cellular phone 7400 illustrated inFIG. 4D is touched with a finger or the like, data can be input into thecellular phone. Further, operations such as making a call and creatingan e-mail can be performed by touching the display portion 7402 with afinger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting information such ascharacters. The third mode is a display-and-input mode in which twomodes of the display mode and the input mode are combined.

For example, in the case of making a call or creating e-mail, the inputmode mainly for inputting characters is selected for the display portion7402 so that characters displayed on the screen can be input.

When a sensing device including a sensor such as a gyroscope sensor oran acceleration sensor for detecting inclination is provided inside thecellular phone 7400, display on the screen of the display portion 7402can be automatically changed in direction by determining the orientationof the cellular phone 7400 (whether the cellular phone 7400 is placedhorizontally or vertically for a landscape mode or a portrait mode).

The screen modes are changed by touch on the display portion 7402 oroperation with the operation button 7403 of the housing 7401. The screenmodes can be switched depending on the kind of images displayed on thedisplay portion 7402. For example, when a signal of an image displayedon the display portion is a signal of moving image data, the screen modeis switched to the display mode. When the signal is a signal of textdata, the screen mode is switched to the input mode.

Moreover, in the input mode, if a signal detected by an optical sensorin the display portion 7402 is detected and the input by touch on thedisplay portion 7402 is not performed for a certain period, the screenmode may be controlled so as to be changed from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by thedisplay portion 7402 while in touch with the palm or the finger, wherebypersonal authentication can be performed. Further, when a backlight or asensing light source which emits near-infrared light is provided in thedisplay portion, an image of a finger vein, a palm vein, or the like canbe taken.

FIG. 4E illustrates an example of a foldable tablet terminal (in an openstate). A tablet terminal 7500 includes a housing 7501 a, a housing 7501b, a display portion 7502 a, and a display portion 7502 b. The housing7501 a and the housing 7501 b are connected by a hinge 7503 and can beopened and closed using the hinge 7503 as an axis. The housing 7501 aincludes a power switch 7504, operation keys 7505, a speaker 7506, andthe like. Note that the tablet terminal 7500 is manufactured by usingthe light-emitting device of one embodiment of the present invention foreither the display portion 7502 a or the display portion 7502 b, orboth.

Part of the display portion 7502 a or the display portion 7502 b can beused as a touch panel region, where data can be input by touchingdisplayed operation keys. For example, a keyboard can be displayed onthe entire region of the display portion 7502 a so that the displayportion 7502 a is used as a touch screen, and the display portion 7502 bcan be used as a display screen.

An indoor lighting device 7601, a roll-type lighting device 7602, a desklamp 7603, and a planar lighting device 7604 illustrated in FIG. 5A areeach an example of a lighting device which includes the light-emittingdevice of one embodiment of the present invention. Since thelight-emitting device of one embodiment of the present invention canhave a larger area, it can be used as a large-area lighting device.Further, since the light-emitting device is thin, the light-emittingdevice can be mounted on a wall.

A desk lamp illustrated in FIG. 5B includes a lighting portion 7701, asupport 7703, a support base 7705, and the like. The light-emittingdevice of one embodiment of the present invention is used for thelighting portion 7701. In one embodiment of the present invention, alighting device whose light-emitting portion has a curved surface or alighting device including a flexible lighting portion can be achieved.Such use of a flexible light-emitting device for a lighting deviceenables a place having a curved surface, such as the ceiling ordashboard of a motor vehicle, to be provided with the lighting device,as well as increases the degree of freedom in design of the lightingdevice.

This embodiment can be combined with any of the other embodiments asappropriate.

Example 1

In this example, a light-emitting element of one embodiment of thepresent invention is described referring to FIG. 6. Chemical formulae ofmaterials used in this example are shown below.

A method for fabricating a light-emitting element 1 of this example isdescribed below.

(Light-Emitting Element 1)

A film of indium tin oxide containing silicon (ITSO) was formed over aglass substrate 1100 by a sputtering method, so that a first electrode1101 functioning as an anode was fruited. The thickness was 110 nm andthe electrode area was 2 mm×2 mm.

Next, as pretreatment for forming the light-emitting element over theglass substrate 1100, UV-ozone treatment was performed for 370 secondsafter washing of a surface of the glass substrate 1100 with water andbaking that was performed at 200° C. for 1 hour.

After that, the glass substrate 1100 was transferred into a vacuumevaporation apparatus where the pressure had been reduced toapproximately 10⁻⁴ Pa, and was subjected to vacuum baking at 170° C. for30 minutes in a heating chamber of the vacuum evaporation apparatus, andthen the glass substrate 1100 was cooled down for about 30 minutes.

Next, the glass substrate 1100 was fixed to a substrate holder in avacuum evaporation apparatus so that a surface of the glass substrate1100 on which the first anode 1101 was formed faced downward. Thepressure in the vacuum evaporation apparatus was reduced to about 10⁻⁴Pa. Then, on the first anode 1101,4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB) andmolybdenum(VI) oxide were deposited by co-evaporation to form ahole-injection layer 1111. The thickness of the layer 1111 was 50 nm,and the ratio of NPB to molybdenum(VI) oxide was adjusted to be 4:1(=NPB:molybdenum oxide) in weight ratio. Note that a co-evaporationmethod refers to an evaporation method in which evaporation is carriedout from a plurality of evaporation sources at the same time in onetreatment chamber.

Next, on the hole-injection layer 1111, a film ofN-phenyl-N-(4-phenylphenyl)-N-(9-phenyl-9H-carbazol-3-yl)amine(abbreviation: PCA1BP) was formed to a thickness of 10 nm, whereby ahole-transport layer 1112 was formed.

Next, 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation:CzPA) andN,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S) were deposited by co-evaporation, whereby alight-emitting layer 1113 was formed on the hole-transport layer 1112.Here, the weight ratio of CzPA to YGA2S was adjusted to be 1:0.04(=CzPA:YGA2S). The thickness of the light-emitting layer 1113 was 30 nm.

Next, a film of tris(8-quinolinolato)aluminum(III) (abbreviation: Alq)was formed to a thickness of 20 nm on the light-emitting layer 1113,whereby an electron-transport layer 1114 was formed.

Then, a film of bathophenanthroline (abbreviation: BPhen) was formed toa thickness of 10 nm on the electron-transport layer 1114, and further,a film of lithium fluoride (LiF) was formed to a thickness of 1 nm byevaporation, whereby an electron-injection layer 1115 was formed.

Lastly, a film of aluminum was formed to a thickness of 200 nm byevaporation, whereby a second electrode 1103 functioning as a cathodewas formed. Thus, the light-emitting element 1 of this example wasfabricated.

Note that, in the above evaporation process, evaporation was allperformed by a resistance heating method.

Table 1 shows the element structure of the light-emitting element ofthis example which was fabricated in the above manner.

TABLE 1 Hole- Hole- Light- Electron- Electron- First injection transportemitting transport injection Second electrode Layer layer layer layerlayer electrode Light-emitting ITSO NPB:MoOx PCA1BP CzPA:YGA2S Alq BPhenLiF Al element 1 110 nm (=4:1) 10 nm (=1:0.04) 20 nm 10 nm 1 nm 200 nm50 nm 30 nm

The light-emitting element 1 was sealed in a glove box containing anitrogen atmosphere so as not to be exposed to the air (specifically, asealant was applied onto outer edge of the element and heat treatmentwas performed at 80° C. for 1 hour at the time of sealing). Then, theoperating characteristics of the light-emitting element 1 were measured.Note that the measurement was carried out at room temperature (in anatmosphere kept at 25° C.).

FIG. 7, FIG. 8, FIG. 9, and FIG. 10 show voltage vs. luminancecharacteristics, luminance vs. current efficiency characteristics,voltage vs. current characteristics, and luminance vs. chromaticitycharacteristics, respectively, of the light-emitting element 1.

It can be found from FIG. 7 and FIG. 8 that the light-emitting element 1is a highly efficient element consuming low power. It can be found fromFIG. 9 that the light-emitting element 1 is an element driven with lowvoltage. It can be found from FIG. 10 that the light-emitting element 1has favorable carrier balance at any luminance.

Table 2 shows initial values of main characteristics of thelight-emitting element 1 at a luminance of about 1000 cd/m².

TABLE 2 Volt- Cur- Current Chroma- Current Power age rent density ticityefficiency efficiency (V) (mA) (mA/cm²) (x, y) (cd/A) (lm/W) Light- 4.61.1 27 (0.16, 0.22) 3.5 2.4 emitting element 1

The above results show that the light-emitting element 1 has highluminance and high current efficiency. Moreover, as for color purity, itcan be found that the light-emitting element exhibits blue emission withexcellent color purity.

FIG. 11 shows an emission spectrum when a current at a current densityof 25 mA/cm² was supplied to the light-emitting element 1. As shown inFIG. 11, the emission spectrum of the light-emitting element 1 has peaksat around 445 nm and 476 nm and it is suggested that the peaks arederived from emission of YGA2S included in the light-emitting layer1113.

The results of this example indicate that PCA1BP can be suitably usedfor the hole-transport layer of the light-emitting element which emitsfluorescence in the visible region.

Example 2

In this example, a light-emitting element of one embodiment of thepresent invention is described referring to FIG. 6. Chemical formulae ofmaterials used in this example are shown below. Note that the materialsthe chemical formulae of which are described above will be omitted.

A method for fabricating a light-emitting element 2 of this example isdescribed below.

(Light-Emitting Element 2)

The first electrode 1101, the hole-injection layer 1111, and thehole-transport layer 1112 were formed on the glass substrate 1100 underconditions similar to those of the light-emitting element 1. Note thatthe ratio of NPB to molybdenum oxide in the hole-injection layer 1111was adjusted to be 4:2 (=NPB:molybdenum oxide) in weight ratio.

Next, 3-phenyl-9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole(abbreviation: CO11II), PCA1BP, andbis{2-(4-fluorophenyl)-3,5-dimethylpyrazinato}(picolinato)iridium(III)(abbreviation: [Ir(dmFppr)₂(pic)]) were deposited by co-evaporation,whereby the light-emitting layer 1113 was formed on the hole-transportlayer 1112. Here, the weight ratio of CO11II to PCA1BP and[Ir(dmFppr)₂(pic)] was adjusted to be 1:0.15:0.1 (=CO11II: PCA1BP:[Ir(dmFppr)₂(pic)]). The thickness of the light-emitting layer 1113 was40 nm.

Next, a film of Alq was formed to a thickness of 10 nm on thelight-emitting layer 1113, whereby the electron-transport layer 1114 wasformed.

Then, a film of BPhen was formed to a thickness of 20 nm on theelectron-transport layer 1114, and further, a film of LiF was formed toa thickness of 1 nm by evaporation, whereby the electron-injection layer1115 was formed.

Lastly, a film of aluminum was formed to a thickness of 200 nm byevaporation, whereby the second electrode 1103 functioning as a cathodewas formed. Thus, the light-emitting element 2 of this example wasfabricated.

Note that, in the above evaporation process, evaporation was allperformed by a resistance heating method.

Table 3 shows the element structure of the light-emitting element ofthis example which was fabricated in the above manner.

TABLE 3 Hole- Hole- Electron- Electron- First injection transporttransport injection Second electrode Layer layer Light-emitting layerlayer layer electrode Light-emitting ITSO NPB:MoOx PCA1BPCO11II:PCA1BP:Ir(dmFppr)₂(pic) Alq BPhen LiF Al element 2 110 nm (=4:2)10 nm (=1:10.15:0.1) 10 nm 20 nm 1 nm 200 nm 50 nm 40 nm

The light-emitting element 2 was sealed in a glove box containing anitrogen atmosphere so as not to be exposed to the air (specifically, asealant was applied onto outer edge of the element and heat treatmentwas performed at 80° C. for 1 hour at the time of sealing). Then, theoperating characteristics of the light-emitting element 2 were measured.Note that the measurement was carried out at room temperature (in anatmosphere kept at 25° C.).

FIG. 12, FIG. 13, FIG. 14, and FIG. 15 show voltage vs. luminancecharacteristics, luminance vs. current efficiency characteristics,voltage vs. current characteristics, and luminance vs. chromaticitycharacteristics, respectively, of the light-emitting element 2.

It can be found from FIG. 12 and FIG. 13 that the light-emitting element2 is a highly efficient element consuming low power. It can be foundfrom FIG. 14 that the light-emitting element 2 is an element driven withlow voltage. It can be found from FIG. 15 that the light-emittingelement 2 has favorable carrier balance at any luminance.

Table 4 shows initial values of main characteristics of thelight-emitting element 2 at a luminance of about 1000 cd/m².

TABLE 4 Volt- Cur- Current Chroma- Current Power age rent density ticityefficiency efficiency (V) (mA) (mA/cm²) (x, y) (cd/A) (lm/W) Light- 4.40.065 1.6 (0.40, 0.58) 61 43 emitting element 2

The above results show that the light-emitting element 2 has highluminance and high current efficiency. Moreover, as for color purity, itcan be found that the light-emitting element exhibits yellow emissionwith excellent color purity.

FIG. 16 shows an emission spectrum when a current at a current densityof 25 mA/cm² was supplied to the light-emitting element 2. As shown inFIG. 16, the emission spectrum of the light-emitting element 2 has apeak at around 550 nm and it is suggested that the peak is derived fromemission of [Ir(dmFppr)₂(pic)] included in the light-emitting layer1113.

FIG. 17 shows results of a reliability test of the light-emittingelement 2. Note that in the reliability test, the light-emitting element2 was driven under the conditions where the initial luminance was set to1000 cd/m² and the current density was constant. The light-emittingelement 2 kept about 86% of the initial luminance after 100 hourselapsed. Thus, the reliability test revealed high reliability of thelight-emitting element 2.

The results of this example indicate that PCA1BP may be used for thehost material of the light-emitting layer and the hole-transport layerof the light-emitting element which emits phosphorescence with awavelength longer than or equal to that of yellow light.

Example 3

In this example, a light-emitting element of one embodiment of thepresent invention is described referring to FIG. 6. Chemical formulae ofmaterials used in this example are shown below. Note that the materialsthe chemical formulae of which are described above will be omitted.

A method for fabricating a light-emitting element 3 of this example isdescribed below.

(Light-Emitting Element 3)

The first electrode 1101 and the hole-injection layer 1111 were foil redon the glass substrate 1100 under conditions similar to those of thelight-emitting element 1.

Next, on the hole-injection layer 1111, a film ofN,N-di(biphenyl-4-yl)-N-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation:PCzBBA1) was formed to a thickness of 10 nm, whereby the hole-transportlayer 1112 was formed.

Next, CzPA and4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA) were deposited by co-evaporation, whereby thelight-emitting layer 1113 was formed on the hole-transport layer 1112.Here, the weight ratio of CzPA to YGAPA was adjusted to be 1:0.04(=CzPA:YGAPA). The thickness of the light-emitting layer 1113 was 30 nm.

Next, a film of Alq was formed to a thickness of 30 nm on thelight-emitting layer 1113, whereby the electron-transport layer 1114 wasformed.

Then, a film of LiF was formed to a thickness of 1 nm on theelectron-transport layer 1114 by evaporation, whereby theelectron-injection layer 1115 was formed.

Lastly, a film of aluminum was formed to a thickness of 200 nm byevaporation, whereby the second electrode 1103 functioning as a cathodewas formed. Thus, the light-emitting element 3 of this example wasfabricated.

Note that, in the above evaporation process, evaporation was allperformed by a resistance heating method.

Table 5 shows the element structure of the light-emitting element ofthis example which was fabricated in the above manner.

TABLE 5 Hole- Hole- Light- Electron- Electron- First injection transportemitting transport injection Second electrode Layer layer layer layerlayer electrode Light-emitting ITSO NPB:MoOx PCzBBA1 CzPA:YGAPA Alq LiFAl element 3 110 nm (=4:1) 10 nm (=1:0.04) 30 nm 10 nm 200 nm 50 nm 30nm

The light-emitting element 3 was sealed in a glove box containing anitrogen atmosphere so as not to be exposed to the air (specifically, asealant was applied onto outer edge of the element and heat treatmentwas performed at 80° C. for 1 hour at the time of sealing). Then, theoperating characteristics of the light-emitting element 3 were measured.Note that the measurement was carried out at room temperature (in anatmosphere kept at 25° C.).

FIG. 18, FIG. 19, FIG. 20, and FIG. 21 show voltage vs. luminancecharacteristics, luminance vs. current efficiency characteristics,voltage vs. current characteristics, and luminance vs. chromaticitycharacteristics, respectively, of the light-emitting element 3.

It can be found from FIG. 18 and FIG. 19 that the light-emitting element3 is a highly efficient element consuming low power. It can be foundfrom FIG. 20 that the light-emitting element 3 is an element driven withlow voltage. It can be found from FIG. 21 that the light-emittingelement 3 has favorable carrier balance at any luminance.

Table 6 below shows initial values of main characteristics of thelight-emitting element 3 at a luminance of about 1000 cd/m².

TABLE 6 Volt- Cur- Current Chroma- Current Power age rent density ticityefficiency efficiency (V) (mA) (mA/cm²) (x, y) (cd/A) (lm/W) Light- 7.42.6 66 (0.17, 0.15) 1.5 0.65 emitting element 3

The above results show that the light-emitting element 3 has highluminance and high current efficiency. Moreover, as for color purity, itcan be found that the light-emitting element exhibits blue emission withexcellent color purity.

FIG. 22 shows an emission spectrum when a current at a current densityof 25 mA/cm² was supplied to the light-emitting element 3. As shown inFIG. 22, the emission spectrum of the light-emitting element 3 has apeak at around 453 nm and it is suggested that the peak is derived fromemission of YGAPA included in the light-emitting layer 1113.

The results of this example show that PCzBBA1 can be suitably used forthe hole-transport layer of the light-emitting element which emitsfluorescence in a visible region.

Example 4

In this example, a light-emitting element of one embodiment of thepresent invention is described referring to FIG. 6. Chemical formulae ofmaterials used in this example are shown below. Note that the materialsthe chemical formulae of which are described above will be omitted.

A method for fabricating a light-emitting element 4 of this example isdescribed below.

(Light-Emitting Element 4)

The first electrode 1101 and the hole-injection layer 1111 were formedon the glass substrate 1100 under conditions similar to those of thelight-emitting element 1.

Next, on the hole-injection layer 1111, a film of PCzBBA1 was formed toa thickness of 10 nm, whereby the hole-transport layer 1112 was formed.

Next, Alq and coumarin 6 were deposited by co-evaporation, whereby thelight-emitting layer 1113 was formed on the hole-transport layer 1112.Here, the weight ratio of Alq to coumarin 6 was adjusted to be 1:0.01(=Alq:coumarin 6). The thickness of the light-emitting layer 1113 was 40nm.

Next, a film of Alq was formed to a thickness of 30 nm on thelight-emitting layer 1113, whereby the electron-transport layer 1114 wasformed.

Then, a film of LiF was formed to a thickness of 1 nm on theelectron-transport layer 1114 by evaporation, whereby theelectron-injection layer 1115 was formed.

Lastly, a film of aluminum was formed to a thickness of 200 nm byevaporation, whereby the second electrode 1103 functioning as a cathodewas formed. Thus, the light-emitting element 4 of this example wasfabricated.

Note that, in the above evaporation process, evaporation was allperformed by a resistance heating method.

Table 7 shows the element structure of the light-emitting element ofthis example which was fabricated in the above manner.

TABLE 7 Hole- Hole- Light- Electron- Electron- First injection transportemitting transport injection Second electrode Layer layer layer layerlayer electrode Light-emitting ITSO NPB:MoOx PCzBBA1 Alq:coumarin6 AlqLiF Al element 4 110 nm (=4:1) 10 nm (=1:0.01) 30 nm 1 nm 200 nm 50 nm40 nm

The light-emitting element 4 was sealed in a glove box containing anitrogen atmosphere so as not to be exposed to the air (specifically, asealant was applied onto outer edge of the element and heat treatmentwas performed at 80° C. for 1 hour at the time of sealing). Then, theoperating characteristics of the light-emitting element 4 were measured.Note that the measurement was carried out at room temperature (in anatmosphere kept at 25° C.).

FIG. 23, FIG. 24, FIG. 25, and FIG. 26 show voltage vs. luminancecharacteristics, luminance vs. current efficiency characteristics,voltage vs. current characteristics, and luminance vs. chromaticitycharacteristics, respectively, of the light-emitting element 4.

It can be found from FIG. 23 and FIG. 24 that the light-emitting element4 is a highly efficient element consuming low power. It can be foundfrom FIG. 25 that the light-emitting element 4 is an element driven withlow voltage. It can be found from FIG. 26 that the light-emittingelement 4 has favorable carrier balance at any luminance.

Table 8 below shows initial values of main characteristics of thelight-emitting element 4 at a luminance of about 1000 cd/m².

TABLE 8 Volt- Cur- Current Chroma- Current Power age rent density ticityefficiency efficiency (V) (mA) (mA/cm²) (x, y) (cd/A) (lm/W) Light- 6.40.33 8.3 (0.31, 0.62) 10 5.0 emitting element 4

The above results show that the light-emitting element 4 has highluminance and high current efficiency. Moreover, as for color purity, itcan be found that the light-emitting element exhibits green emissionwith excellent color purity.

FIG. 27 shows an emission spectrum when a current at a current densityof 25 mA/cm² was supplied to the light-emitting element 4. As shown inFIG. 27, the emission spectrum of the light-emitting element 4 has apeak at around 517 nm and it is suggested that the peak is derived fromemission of coumarin 6 included in the light-emitting layer 1113.

The results of this example show that PCzBBA1 can be suitably used forthe hole-transport layer of the light-emitting element which emitsfluorescence in a visible region.

Example 5

This example shows the synthesis of an organic compound included in alight-emitting element of one embodiment of the present invention andresults of evaluation of characteristics thereof.

Synthesis Example 1

Described is a method for synthesizingN-phenyl-N-(4-phenylphenyl)-N-(9-phenyl-9H-carbazol-3-yl)amine(abbreviation: PCA1BP) represented by a structural formula (100) below.

Into a 200 mL three-neck flask were put 3.2 g (10 mmol) of3-bromo-9-phenyl-9H-carbazole, 2.5 g (10 mmol) of4-phenyl-diphenylamine, 1.5 g (15 mmol) of sodium tert-butoxide, and 0.1g (0.2 mmol) of bis(dibenzylideneacetone)palladium(0), and the air inthe flask was replaced with nitrogen. Then, 20 mL of dehydrated xylenewas added to this mixture. After the mixture was deaerated while beingstirred under reduced pressure, 1.2 mL (0.6 mmol) oftri(tert-butyl)phosphine (10 wt % hexane solution) was added thereto.This mixture was stirred under a nitrogen atmosphere at 110° C. for 6.5hours to be reacted.

After the reaction, 400 mL of toluene was added to the reaction mixturesolution, and the resulting suspension was filtrated through Florisil(produced by Wako Pure Chemical Industries, Ltd., Catalog No.540-00135), alumina, and Celite (produced by Wako Pure ChemicalIndustries, Ltd., Catalog No. 531-16855). The obtained filtrate wasconcentrated, and methanol was added thereto. The mixture was irradiatedwith supersonic and then recrystallized to obtain 4.4 g of an objectivelight-yellow powder at a yield of 91%. A synthesis scheme (a) thereof isshown below.

The Rf values of the objective substance, 3-bromo-9-phenyl-9H-carbazole,and 4-phenyl-diphenylamine were respectively 0.65, 0.73, and 0.54, whichwere obtained by silica gel thin layer chromatography (TLC) (with adeveloping solvent containing ethyl acetate and hexane in a 1:5 ratio).

This compound was identified as PCA1BP, which was the object of thesynthesis, by nuclear magnetic resonance (NMR) spectroscopy.

¹H NMR data of the obtained substance are as follows: ¹H-NMR (DMSO-d6,300 MHz): δ (ppm)=7.00-7.11 (m, 5H), 7.21-7.44 (m, 10H), 7.54-7.71 (m,9H), 8.06 (d, J=1.8 Hz, 1H), 8.17 (d, J=7.2 Hz, 1H).

FIGS. 28A and 28B show ¹H NMR charts. Note that FIG. 28B is a chartshowing an enlarged part of FIG. 28A in the range of 6.00 ppm to 9.00ppm.

FIG. 29A shows an absorption spectrum and an emission spectrum of atoluene solution (0.120 mmol/L) of PCA1BP. FIG. 29B shows an absorptionspectrum and an emission spectrum of a thin film of PCA1BP. Theabsorption spectrum was measured with a UV-visible spectrophotometer(V-550, manufactured by JASCO Corporation). The measurements wereperformed with samples prepared in such a manner that the solution wasput in a quartz cell and the thin film was obtained by evaporation ontoa quartz substrate. The absorption spectrum of the solution was obtainedby subtracting the absorption spectra of quartz and toluene from thoseof quartz and the solution, and the absorption spectrum of the thin filmwas obtained by subtracting the absorption spectrum of a quartzsubstrate from those of the quartz substrate and the thin film. In thecase of the toluene solution, the absorption peak was observed at around321 nm, and the maximum emission wavelength was 415 nm (excitationwavelength: 325 nm). In the case of the thin film, the absorption peakwas observed at around 323 nm, and the maximum emission wavelength was421 nm (excitation wavelength: 312 nm).

Further, a HOMO level and a LUMO level of PCA1BP were obtained by cyclicvoltammetry (CV) measurement. An electrochemical analyzer (ALS model600A or 600C, manufactured by BAS Inc.) was used for the CV measurement.

Further, as for a solution used for the CV measurement, dehydrateddimethylformamide (DMF, manufactured by Sigma-Aldrich Inc., 99.8%,Catalog No. 22705-6) was used as a solvent, and tetra-n-butylammoniumperchlorate (n-Bu₄NClO₄, manufactured by Tokyo Chemical Industry Co.,Ltd., Catalog No. T0836), which was a supporting electrolyte, wasdissolved in the solvent such that the concentration oftetra-n-butylammonium perchlorate was 100 mmol/L. Further, the object tobe measured was dissolved in the solvent such that the concentrationthereof was 2 mmol/L. A platinum electrode (manufactured by BAS Inc.,PTE platinum electrode) was used as a working electrode, a platinumelectrode (manufactured by BAS Inc., Pt counter electrode for VC-3, (5cm)) was used as an auxiliary electrode, and an Ag/Ag⁺ electrode(manufactured by BAS Inc., RE-7 reference electrode for nonaqueoussolvent) was used as a reference electrode. The CV measurement wasperformed under the following conditions: room temperature (20° C. to25° C.) and a scan rate of 0.1 V/sec. Note that the potential energy ofthe reference electrode with respect to the vacuum level was assumed tobe −4.94 eV in this example.

On the assumption that the intermediate potential (the half-wavepotential) between the oxidation peak potential E_(pa) and the reductionpeak potential E_(pe) which are obtained in the CV measurementcorresponds to the HOMO level, the HOMO level of PCA1BP was calculatedto be −5.31 eV, and the LUMO level of PCA1BP was calculated to be −2.12eV. Accordingly, the band gap (ΔE) of PCA1BP was found to be 3.19 eV.

In addition, the oxidation peak took a similar value even after the 100cycles. This indicates that PCA1BP has properties effective againstrepetition of redox reactions between an oxidized state and a neutralstate.

Furthermore, PCA1BP was subjected to mass spectrometric (MS) analysis byLC/MS.

The analysis by LC/MS was carried out with Acquity UPLC (manufactured byWaters Corporation), and Xevo G2 Tof MS (manufactured by WatersCorporation). In the MS, ionization was carried out by an electrosprayionization (abbreviation: ESI) method. At this time, the capillaryvoltage and the sample cone voltage were set to 3.0 kV and 30 V,respectively, and detection was performed in a positive mode. Acomponent which underwent the ionization under the above conditions wasmade to collide with an argon gas in a collision cell to dissociate intoproduct ions. Energy (collision energy) for the collision with argon was6 eV, 30 eV and 50 eV. A mass range for the measurement was m/z100-1200. FIG. 30A shows the measurement results in the case of acollision energy of 6 eV. FIG. 30B shows the measurement results in thecase of a collision energy of 50 eV.

In FIG. 30A, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from precursor ions of PCA1BP aredetected mainly around m/z=487 when the collision energy is 6 eV.Further, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from product ions of PCA1BP aredetected mainly around m/z=246 and around m/z=262. Also, owing to thepresence and absence of hydrogen ions and isotopes, a peak derived fromproduct ions of PCA1BP are detected mainly around m/z=246 when thecollision energy is 30 eV, though not shown.

The product ion detected around m/z=246 can be regarded as being derivedfrom a proton adduct of a cation in a state where phenylcarbazole iseliminated from PCA1BP, and is one of characteristic product ionsrepresenting an organic compound having the phenylcarbazole.

Further, the product ion detected around m/z=246 can also be regarded asbeing derived from a radical cation of an N-phenyl-N-phenylamine, andcan be one of characteristic product ions representing an organiccompound having the phenylcarbazole and the N-phenyl-N-phenylamine.

In FIG. 30B, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from precursor ions of PCA1BP aredetected mainly around m/z=487 when the collision energy is 50 eV.Further, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from product ions of PCA1BP aredetected mainly around m/z=169, around m/z=243, around m/z=257, aroundm/z=334, and around m/z=410.

The product ion detected around m/z=243 can be regarded as being derivedfrom a proton adduct of a radical cation at the 3-position ofphenylcarbazole and is one of characteristic product ions representingan organic compound having the phenylcarbazole.

The results in FIGS. 30A and 30B are characteristically derived fromPCA1BP and thus can be regarded as important data in identification ofPCA1BP contained in the light-emitting element.

Measurement of PCA1BP with a TOF-SIMS was further performed, and FIGS.31A and 31B and FIGS. 32A and 32B show the qualitative spectra (positiveions and negative ions). Note that FIGS. 31A and 31B show measurementresults in the case of positive ions, and FIGS. 32A and 32B showmeasurement results in the case of negative ions. In each of FIGS. 31Aand 32A, the horizontal axis represents m/z in the range of 0 to 450,and the vertical axis represents intensity (arbitrary unit). In each ofFIGS. 31B and 32B, the horizontal axis represents m/z in the range of450 to 1200, and the vertical axis represents intensity (arbitraryunit).

TOF.SIMS 5 (manufactured by ION-TOF GmbH) was used, where Bi₃ ⁺⁺ wasused as a primary ion. Note that irradiation with the primary ions wasperformed in a pulsed manner with a pulse width of 7 ns to 12 ns. Theirradiation amount was greater than or equal to 8.2×10¹⁰ ions/cm² andless than or equal to 6.7×10¹¹ ions/cm² (less than or equal to 1×10¹²ions/cm²), the acceleration voltage was 25 keV, and the current valuewas 0.2 pA. A powder of PCA1BP was a sample used for the measurement.

The results in FIGS. 31A and 31B reveal that, owing to the presence andabsence of hydrogen ions and isotopes, PCA1BP mainly has a plurality ofpeaks derived from precursor ions around m/z=486, a plurality of peaksderived from product ions around m/z=243, and a plurality of peaksderived from adducts around m/z=499. The results in FIGS. 32A and 32Breveal that, owing to the presence and absence of hydrogen ions andisotopes, PCA1BP mainly has a plurality of peaks derived from precursorions around m/z=485, a plurality of peaks derived from product ionsaround m/z=26, around m/z=409, and around m/z=473, and a plurality ofpeaks derived from adducts around m/z=497. Note that the measurementresults with a TOF-SIMS can be similarly regarded as important data inidentification of PCA1BP contained in the light-emitting element.

As described above, a peak of a product ion detected around m/z=243which is one of characteristic product ions representing an organiccompound having the phenylcarbazole can be observed also in the resultof the measurement with the TOF-SIMS.

Synthesis Example 2

Described is a method for synthesizingN,N-di(biphenyl-4-yl)-N-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation:PCzBBA1) represented by a structural formula (101) below.

Into a 200 mL three-neck flask were put 3.7 g (10 mmol) of3-iodo-9-phenyl-9H-carbazole, 3.2 g (10 mmol) of4,4′-diphenyldiphenylamine, 1.5 g (15 mmol) of sodium tert-butoxide, and0.1 g (0.2 mmol) of bis(dibenzylideneacetone)palladium(0), and the airin the flask was replaced with nitrogen. Then, 25 mL of dehydratedxylene was added to this mixture. After the mixture was deaerated whilebeing stirred under reduced pressure, 1.2 mL (0.6 mmol) oftri(tert-butyl)phosphine (10 wt % hexane solution) was added thereto.This mixture was stirred under a nitrogen atmosphere at 110° C. for 4.5hours to be reacted.

After the reaction, 200 mL of toluene was added to this reactionmixture, and this suspension was filtrated through Florisil, alumina,and then Celite. The obtained filtrate was concentrated and thenrecrystallized to obtain 3.7 g of an objective light-yellow powder at ayield of 66%. A synthesis scheme (b) thereof is shown below.

The Rf values of the objective substance, 3-iodo-9-phenyl-9H-carbazole,and 4,4′-diphenyldiphenylamine were respectively 0.43, 0.59, and 0.19,which were obtained by silica gel thin layer chromatography (TLC) (witha developing solvent containing ethyl acetate and hexane in a 1:10ratio).

This compound was identified as PCzBBA1, which was the object of thesynthesis, by nuclear magnetic resonance (NMR) spectroscopy.

¹H NMR data of the obtained substance are as follows: ¹H-NMR (DMSO-d6,300 MHz): δ (ppm)=7.14 (d, J=8.1 Hz, 4H), 7.22-7.46 (m, 11H), 7.53-7.73(m, 13H), 8.15 (s, 1H), 8.23 (d, J=7.8 Hz, 1H).

FIGS. 33A and 33B show ¹H NMR charts. Note that FIG. 33B is a chartshowing an enlarged part of FIG. 33A in the range of 6.00 ppm to 9.00ppm.

FIG. 34A shows an absorption spectrum and an emission spectrum of atoluene solution (0.120 mmol/L) of PCzBBA1. FIG. 34B shows an absorptionspectrum and an emission spectrum of a thin film of PCzBBA1. Themeasurement was performed using conditions and a method which weresimilar to those in Synthesis Example 1. In the case of the toluenesolution, the absorption peak was observed at around 330 nm, and themaximum emission wavelength was 415 nm (excitation wavelength: 330 nm).In the case of the thin film, the absorption peak was observed at around335 nm, and the maximum emission wavelength was 441 nm (excitationwavelength: 335 nm).

Further, a HOMO level and a LUMO level of PCzBBA1 were obtained bycyclic voltammetry (CV) measurement. When the measurement was performedusing conditions and a method which were similar to those in SynthesisExample 1, the HOMO level of PCzBBA1 was calculated to be −5.28 eV, andthe LUMO level of PCzBBA1 was calculated to be −2.30 eV. Thus, the bandgap (ΔE) of PCzBBA1 was found to be 2.98 eV. In addition, the oxidationpeak took a similar value even after the 100 cycles. This indicates thatPCzBBA1 has properties effective against repetition of redox reactionsbetween an oxidized state and a neutral state.

Further, PCzBBA1 was subjected to MS analysis by LC/MS.

The LC/MS was conducted using an apparatus, a method, and conditionswhich were similar to those in the case of PCA1BP. FIG. 35A shows themeasurement results in the case of a collision energy of 6 eV. FIG. 35Bshows the measurement results in the case of a collision energy of 50eV.

In FIG. 35A, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from precursor ions of PCzBBA1are detected mainly around m/z=563 when the collision energy is 6 eV.Further, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from product ions are detectedmainly around m/z=322 and around in/z=338.

The product ion detected around m/z=322 can be regarded as being derivedfrom a proton adduct of a cation in a state where phenylcarbazole iseliminated from PCzBBA1, and is one of characteristic product ionsrepresenting an organic compound having the phenylcarbazole.

Further, the product ion detected around m/z=322 can also be regarded asbeing derived from a radical cation of an N,N-bis-biphenylamine, and canbe one of characteristic product ions representing an organic compoundhaving the phenylcarbazole and the N,N-bis-biphenylamine.

In FIG. 35B, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from precursor ions of PCzBBA1are detected mainly around m/z=563 when the collision energy is 50 eV.Further, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks are detected mainly around m/z=169,around m/z=332, around m/z=410, and around m/z=485. The results in FIGS.35A and 35B are characteristically derived from PCzBBA1 and thus can beregarded as important data in identification of PCzBBA1 contained in thelight-emitting element.

Measurement of PCzBBA1 with a TOF-SIMS was further performed, and FIGS.36A and 36B and FIGS. 37A and 37B show the qualitative spectra (positiveions and negative ions). The measurement was performed using anapparatus, a method, and conditions which were similar to those in thecase of PCA1BP.

Note that FIGS. 36A and 36B show measurement results in the case ofpositive ions, and FIGS. 37A and 37B show measurement results in thecase of negative ions. In FIGS. 36A and 37A, the horizontal axisrepresents m/z in the range of 0 to 450, and the vertical axisrepresents intensity (arbitrary unit). In FIGS. 36B and 37B, thehorizontal axis represents m/z in the range of 450 to 1200, and thevertical axis represents intensity (arbitrary unit).

The results in FIGS. 36A and 36B reveal that, owing to the presence andabsence of hydrogen ions and isotopes, PCzBBA1 mainly has a plurality ofpeaks derived from precursor ions around m/z=562, a plurality of peaksderived from product ions around m/z=152, around m/z=243, aroundm/z=320, and around m/z=408, and a plurality of peaks derived fromadducts around m/z=575. The results in FIGS. 37A and 37B reveal that,owing to the presence and absence of hydrogen ions and isotopes, PCzBBA1mainly has a plurality of peaks derived from precursor ions aroundm/z=561, a plurality of peaks derived from product ions around m/z=26,around m/z=485, and around m/z=549, and a plurality of peaks derivedfrom adducts around m/z=573. Note that the measurement results with aTOF-SIMS can be similarly regarded as important data in identificationof PCzBBA1 contained in the light-emitting element.

The product ion detected around m/z=243 can be regarded as being derivedfrom a proton adduct of a radical cation at the 3-position ofphenylcarbazole and is one of characteristic product ions representingan organic compound having the phenylcarbazole.

Comparison Example

Further, N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline(abbreviation: YGA1BP) represented by a structural formula (200) belowwas subjected to MS analysis by LC/MS. Here, YGA1BP is isomeric withPCA1BP shown in Synthesis Example 1.

The LC/MS was conducted using an apparatus, a method, and conditionswhich were similar to those in the case of PCA1BP. FIG. 38A shows themeasurement results in the case of a collision energy of 6 eV. FIG. 38Bshows the measurement results in the case of a collision energy of 50eV.

In FIG. 38A, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from precursor ions of YGA1BP aredetected mainly around m/z=487 when the collision energy is 6 eV.Further, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from product ions are detectedaround m/z=246.

In FIG. 38B, owing to the presence and absence of hydrogen ions andisotopes, a plurality of peaks derived from precursor ions of YGA1BP aredetected mainly around m/z=487 when the collision energy is 50 eV.Further, owing to the presence and absence of hydrogen ions andisotopes, a plurality of product ions are detected mainly aroundm/z=166, m/z=243, m/z=319, m/z=334, and m/z=410. Note that the resultsin FIGS. 38A and 38B are characteristically derived from YGA1BP and thuscan be regarded as important data in identification of YGA1BP containedin the light-emitting element.

By comparing the result of this comparison example (FIG. 38) with theresult of Synthesis Example 1 (FIG. 30), it is revealed that YGA1BP isisomeric with PCA1BP and that YGA1BP and PCA1BP having the samesubstituents (carbazole and N-phenyl-Nphenylamine) show differentintensity ratios.

In particular, when the collision energy is 50 eV, the peak intensity ofa product ion of YGA1BP detected around m/z=243 is high as compared tothe case of PCA1BP; the peak intensity was ¼ or more of the peakintensity derived from a precursor ion. However, as for PCA1BP andPCzBBA1 shown in Synthesis Example 2 (FIG. 35), few peaks are detectedaround m/z=243. Consequently, the peak of the product ion detectedaround m/z=243 can be regarded as being derived from a(9H-carbazole-9-yl)phenyl group contained in YGA1BP. Thus, LC/MSanalysis is effective in differentiating allotropes which are differentfrom each other in a substitution site of a carbazole skeleton.

FIG. 39 shows the results of measuring absorption edges in absorptionspectra of PCA1BP, PCzBBA1, and YGA1BP in Synthesis Examples 1 and 2 andComparison Example. Here, liquid chromatography (LC) separation wascarried out with Acquity UPLC (produced by Waters Corporation). AcquityUPLC BEH C8 (2.1×100 mm, 1.7 μm) was used as a column for the LCseparation, and the column temperature was 40° C. Acetonitrile was usedfor Mobile Phase A and a 0.1% formic acid aqueous solution was used forMobile Phase B. Further, a sample was prepared in such a manner thatPCA1BP, PCzBBA1, or YGA1BP was dissolved in toluene at a givenconcentration and the mixture was diluted with acetonitrile. Theinjection amount was 5.0 μL.

In the LC separation, a gradient method in which the composition ofmobile phases is changed was employed. The ratio of Mobile Phase A toMobile Phase B was 65:25 for 0 to 1 minute immediately after the startof the measurement, and then the composition was changed so that theratio of Mobile Phase A to Mobile Phase B in the 10th minute after thestart of the measurement was 95:5. The composition was changed linearly.

It is found from FIG. 39 that the absorption edges of PCA1BP and PCzBBA1are on a longer wavelength side than the absorption edge of YGA1BP.Specifically, the absorption edges thereof are found to be at 380 nm ormore (3.3 eV or less). It can be said that this is one ofcharacteristics of a carbazole-3-amine skeleton. Thus, as for PCA1BP andPCzBBA1, a band gap between HOMO and LUMO is narrow and excitationenergy is low as compared to YGA1BP. Therefore, it can be said thatPCA1BP and PCzBBA1 are superior in transfer of energy from alight-emitting substance which emits light with a wavelength of about380 nm to about 420 nm to PCA1BP and PCzBBA1. In addition, a peak on thelongest wavelength side of an absorption spectrum of each of PCA1BP andPCzBBA1 was found to be at 300 nm or more.

This application is based on Japanese Patent Application serial no.2012-257369 filed with Japan Patent Office on Nov. 26, 2012, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. (canceled)
 2. A light-emitting device comprising:an electrode; a layer including an organic compound adjacent to theelectrode; and a light-emitting layer, wherein: the organic compound isrepresented by a formula (G1)

R¹ represents hydrogen, an alkyl group having 1 to 6 carbon atoms, or asubstituted or unsubstituted phenyl group, R² to R⁶ separately representhydrogen, an alkyl group having 1 to 6 carbon atoms, a substituted orunsubstituted phenyl group, a substituted or unsubstituted naphthylgroup, or a substituted or unsubstituted phenanthryl group, Ar¹represents hydrogen, a substituted or unsubstituted phenyl group, asubstituted or unsubstituted naphthyl group, or a substituted orunsubstituted phenanthryl group, Ar² represents a substituted orunsubstituted phenyl group, a substituted or unsubstituted naphthylgroup, or a substituted or unsubstituted phenanthryl group, a molecularweight X of the organic compound is greater than or equal to 450 andless than or equal to 1500, an absorption edge of the organic compoundis at 380 nm or more, and a product ion is detected at least aroundm/z=(X−240) by mass spectrometry.
 3. The light-emitting device accordingto claim 2, wherein the organic compound is represented by a formula(G2)


4. The light-emitting device according to claim 3, wherein the organiccompound is represented by a formula (G3)


5. The light-emitting device according to claim 4, wherein the organiccompound is represented by a formula (G4)


6. The light-emitting device according to claim 5, wherein the organiccompound is represented by a formula (100)


7. The light-emitting device according to claim 5, wherein the organiccompound is represented by a formula (101)


8. The light-emitting device according to claim 2, wherein the massspectrometry is liquid chromatography mass spectrometry in a positivemode in which an argon gas is made to collide at any energy higher thanor equal to 1 eV and lower than or equal to 30 eV with the organiccompound.
 9. An electronic device comprising the light-emitting deviceaccording to claim
 2. 10. A light-emitting device comprising: anelectrode; a layer including an organic compound adjacent to theelectrode; and a light-emitting layer, wherein: the organic compoundcomprises a phenylcarbazole skeleton and an N-biphenyl-N-phenylamineskeleton, the N-biphenyl-N-phenylamine skeleton is bonded to a3-position of the phenylcarbazole skeleton, a molecular weight X of theorganic compound is greater than or equal to 450 and less than or equalto 1500, an absorption edge of the organic compound is at 380 nm ormore, and a product ion is detected at least around m/z=(X−240) by massspectrometry.
 11. The light-emitting device according to claim 10,wherein the organic compound is represented by a formula (100)


12. The light-emitting device according to claim 10, wherein the massspectrometry is liquid chromatography mass spectrometry in a positivemode in which an argon gas is made to collide at any energy higher thanor equal to 1 eV and lower than or equal to 30 eV with the organiccompound.
 13. An electronic device comprising the light-emitting deviceaccording to claim 10.